{
  "affected": [
    {
      "affectedData": [
        {
          "defaultStatus": "unaffected",
          "product": "Unbound",
          "vendor": "NLnet Labs",
          "versions": [
            {
              "lessThan": "1.25.2",
              "status": "affected",
              "version": "0",
              "versionType": "semver"
            }
          ]
        }
      ],
      "source": "sep@nlnetlabs.nl"
    }
  ],
  "configurations": [
    {
      "nodes": [
        {
          "cpeMatch": [
            {
              "criteria": "cpe:2.3:a:nlnetlabs:unbound:*:*:*:*:*:*:*:*",
              "matchCriteriaId": "9C01A425-F6D7-49A7-A72D-BF2159564DB6",
              "versionEndExcluding": "1.25.2",
              "vulnerable": true
            }
          ],
          "negate": false,
          "operator": "OR"
        }
      ]
    }
  ],
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "In NLnet Labs Unbound up to and including version 1.25.1, when \u0027unwanted-reply-threshold\u0027 is enabled (set to any value greater than zero), glue records of 0.0.0.0/::0 can short-circuit Unbound, on systems that can direct such traffic, by issuing DNS queries and receiving seemingly unwanted replies since the remote IP does not match the original source IP of 0.0.0.0/::0. This behavior keeps on looping for the glue records and pushing the counter to the configured \u0027unwanted-reply-threshold\u0027 that triggers a defensive cache clear. A malicious actor who controls a delegation that returns in-bailiwick glue of 0.0.0.0/::0 can drive the counter to the limit of \u0027unwanted-reply-threshold\u0027 to the threshold and trigger a cache clean of the message and rrset caches; at will, indefinitely, without sending a single spoofed packet. The iterator uses the 0.0.0.0/::0 glue, and a system that can route this (e.g., Linux kernel routes the datagram over loopback), Unbound\u0027s own listener answers from 127.0.0.1. Because of the mismatch of 0.0.0.0 and 127.0.0.1, in this example, Unbound accounts the reply as an unwanted (probably spoofed) answer. The counter resets to zero on every cache flush, so the attack loops forever."
    },
    {
      "lang": "es",
      "value": "En NLnet Labs Unbound hasta la versi\u00f3n 1.25.1 inclusive, cuando \u2019unwanted-reply-threshold\u2019 est\u00e1 habilitado (establecido a cualquier valor mayor que cero), los registros glue de 0.0.0.0/::0 pueden provocar un cortocircuito en Unbound, en sistemas que pueden dirigir dicho tr\u00e1fico, al emitir consultas DNS y recibir respuestas aparentemente no deseadas ya que la IP remota no coincide con la IP de origen original de 0.0.0.0/::0. Este comportamiento sigue en bucle para los registros glue y empujando el contador al \u2019unwanted-reply-threshold\u2019 configurado que activa una limpieza defensiva de la cach\u00e9. Un actor malicioso que controla una delegaci\u00f3n que devuelve glue in-bailiwick de 0.0.0.0/::0 puede llevar el contador al umbral de \u2019unwanted-reply-threshold\u2019 y activar una limpieza de la cach\u00e9 de mensajes y de los cach\u00e9s de rrset; a voluntad, indefinidamente, sin enviar un solo paquete falsificado. El iterador utiliza el glue 0.0.0.0/::0, y un sistema que puede enrutar esto (por ejemplo, el kernel de Linux enruta el datagrama a trav\u00e9s de loopback), el propio oyente de Unbound responde desde 127.0.0.1. Debido a la falta de coincidencia entre 0.0.0.0 y 127.0.0.1, en este ejemplo, Unbound considera la respuesta como una respuesta no deseada (probablemente falsificada). El contador se restablece a cero en cada vaciado de cach\u00e9, por lo que el ataque se repite indefinidamente."
    }
  ],
  "id": "CVE-2026-50251",
  "lastModified": "2026-10-24T13:10:00.147",
  "metrics": {
    "cvssMetricV31": [
      {
        "cvssData": {
          "attackComplexity": "LOW",
          "attackVector": "NETWORK",
          "availabilityImpact": "LOW",
          "baseScore": 5.3,
          "baseSeverity": "MEDIUM",
          "confidentialityImpact": "NONE",
          "integrityImpact": "NONE",
          "privilegesRequired": "NONE",
          "scope": "UNCHANGED",
          "userInteraction": "NONE",
          "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L",
          "version": "3.1"
        },
        "exploitabilityScore": 3.9,
        "impactScore": 1.4,
        "source": "sep@nlnetlabs.nl",
        "type": "Secondary"
      }
    ],
    "ssvcV203": [
      {
        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "ssvcData": {
          "id": "CVE-2026-50251",
          "options": [
            {
              "exploitation": "none"
            },
            {
              "automatable": "yes"
            },
            {
              "technicalImpact": "partial"
            }
          ],
          "role": "CISA Coordinator",
          "timestamp": "2026-07-22T14:34:31.755779Z",
          "version": "2.0.3"
        }
      }
    ]
  },
  "published": "2026-07-22T14:17:20.503",
  "references": [
    {
      "source": "sep@nlnetlabs.nl",
      "tags": [
        "Vendor Advisory"
      ],
      "url": "https://www.nlnetlabs.nl/downloads/unbound/CVE-2026-50251.txt"
    }
  ],
  "sourceIdentifier": "sep@nlnetlabs.nl",
  "vulnStatus": "Analyzed",
  "weaknesses": [
    {
      "description": [
        {
          "lang": "en",
          "value": "CWE-184"
        }
      ],
      "source": "sep@nlnetlabs.nl",
      "type": "Secondary"
    }
  ]
}

{
  "affected": [],
  "aliases": [
    "CVE-2026-50251"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-184"
    ],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-07-22T14:17:20Z",
    "severity": "MODERATE"
  },
  "details": "In NLnet Labs Unbound up to and including version 1.25.1, when \u0027unwanted-reply-threshold\u0027 is enabled (set to any value greater than zero), glue records of 0.0.0.0/::0 can short-circuit Unbound, on systems that can direct such traffic, by issuing DNS queries and receiving seemingly unwanted replies since the remote IP does not match the original source IP of 0.0.0.0/::0. This behavior keeps on looping for the glue records and pushing the counter to the configured \u0027unwanted-reply-threshold\u0027 that triggers a defensive cache clear. A malicious actor who controls a delegation that returns in-bailiwick glue of 0.0.0.0/::0 can drive the counter to the limit of \u0027unwanted-reply-threshold\u0027 to the threshold and trigger a cache clean of the message and rrset caches; at will, indefinitely, without sending a single spoofed packet. The iterator uses the 0.0.0.0/::0 glue, and a system that can route this (e.g., Linux kernel routes the datagram over loopback), Unbound\u0027s own listener answers from 127.0.0.1. Because of the mismatch of 0.0.0.0 and 127.0.0.1, in this example, Unbound accounts the reply as an unwanted (probably spoofed) answer. The counter resets to zero on every cache flush, so the attack loops forever.",
  "id": "GHSA-rj42-r8f9-w75j",
  "modified": "2026-07-22T15:31:24Z",
  "published": "2026-07-22T15:31:24Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-50251"
    },
    {
      "type": "WEB",
      "url": "https://www.nlnetlabs.nl/downloads/unbound/CVE-2026-50251.txt"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L",
      "type": "CVSS_V3"
    }
  ]
}

{
  "affected": [
    {
      "ecosystem_specific": {
        "aarch64": [
          "python3-unbound-1.13.2-25.oe2203sp4.aarch64.rpm",
          "unbound-1.13.2-25.oe2203sp4.aarch64.rpm",
          "unbound-anchor-1.13.2-25.oe2203sp4.aarch64.rpm",
          "unbound-debuginfo-1.13.2-25.oe2203sp4.aarch64.rpm",
          "unbound-debugsource-1.13.2-25.oe2203sp4.aarch64.rpm",
          "unbound-devel-1.13.2-25.oe2203sp4.aarch64.rpm",
          "unbound-help-1.13.2-25.oe2203sp4.aarch64.rpm",
          "unbound-libs-1.13.2-25.oe2203sp4.aarch64.rpm"
        ],
        "src": [
          "unbound-1.13.2-25.oe2203sp4.src.rpm"
        ],
        "x86_64": [
          "python3-unbound-1.13.2-25.oe2203sp4.x86_64.rpm",
          "unbound-1.13.2-25.oe2203sp4.x86_64.rpm",
          "unbound-anchor-1.13.2-25.oe2203sp4.x86_64.rpm",
          "unbound-debuginfo-1.13.2-25.oe2203sp4.x86_64.rpm",
          "unbound-debugsource-1.13.2-25.oe2203sp4.x86_64.rpm",
          "unbound-devel-1.13.2-25.oe2203sp4.x86_64.rpm",
          "unbound-help-1.13.2-25.oe2203sp4.x86_64.rpm",
          "unbound-libs-1.13.2-25.oe2203sp4.x86_64.rpm"
        ]
      },
      "package": {
        "ecosystem": "openEuler:22.03-LTS-SP4",
        "name": "unbound",
        "purl": "pkg:rpm/openEuler/unbound\u0026distro=openEuler-22.03-LTS-SP4"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "1.13.2-25.oe2203sp4"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "database_specific": {
    "severity": "High"
  },
  "details": "Unbound is a validating, recursive, caching DNS resolver. It is designed to be fast and lean and incorporates modern features based on open standards. To help increase online privacy, Unbound supports DNS-over-TLS which allows clients to encrypt their communication. Unbound is available for most platforms such as FreeBSD, OpenBSD, NetBSD, MacOS, Linux and Microsoft Windows. Unbound is a totally free, open source software under the BSD license. It doesn\u0026amp;apos;t make custom builds or provide specific features to paying customers only.\r\n\r\nSecurity Fix(es):\n\nWith NLnet Labs Unbound up to and including version 1.25.1, applications using libunbound and configured with \u0026apos;unwanted-reply-threshold\u0026apos;, could eventually be abruptly terminated if the threshold is reached and libunbound needs to call \u0026apos;libworker_alloc_cleanup\u0026apos; since the function is absent from the function call allow list. When an application using libunbound sets \u0026apos;unwanted-reply-threshold\u0026apos; to any non-zero value and the iterator queries an authoritative that replies with enough wrong-transaction-ID UDP datagrams to cross the threshold, the \u0026apos;libworker_alloc_cleanup\u0026apos; will eventually be called. Since the function is absent from the function call allow list, this leads to a fatal exit of libunbound and eventual termination of the embedding application.Unbound itself is not affected since its relevant function \u0026apos;worker_alloc_cleanup\u0026apos; is registed in the allow list and proceeds to perform the documented cache flush.(CVE-2026-44621)\n\nIn NLnet Labs Unbound 1.7.0 up to and including 1.25.1, insufficient validation of the RRSIG.Labels field combined with premature cache writes during RFC 8198 aggressive NSEC processing leads to cache poisoning that permits a malicious actor controlling a single delegated zone to poison arbitrary sibling zones under NSEC-signed parent domains. A malicious actor with one registered domain under an NSEC-signed TLD can serve malicious insecure DNS responses for unrelated sibling domains (sharing the same parent zone). Arbitrary delegations that do not exist under the parent domain and are covered by the parent\u0026apos;s NSEC chain can be brought into insecure existence by fraudulent wildcard DS records (less labels than expected, unknown algorithm) from the malicious sibling domain. This allows the malicious actor to inject insecure wildcard records for those delegations.(CVE-2026-44690)\n\nIn NLnet Labs Unbound 1.6.0 up to and including 1.25.1, a replay of a wildcard rrset as another piece of data, could be briefly considered DNSSEC secure based only on the RRSIG validation and stored into cache, before later validation treats it as bogus based on NSEC validation. When the resolving thread puts secure on the rrset, and another thread that is on the serve expired path then picks up the updated rrset contents with the secure status for a reply, it can be used to change a specific record, next to a wildcard that could be covered by the wildcard, into the wildcard. A malicious actor can exploit the possible poisonous effect by having any DNSSEC-singed domain (irrelevant to the victim domain) and a CNAME wrapper record that points to a record next to a wildcard (that could be covered by the wildcard). Then quering Unbound for the wildcard sibling record would seed the secure message. A later (after expiry) query for the CNAME wrapper would need to resolve the target sibling record. If the wildcard replay is injected into the response, the wildcard rrset will update the expired sibling record with a secure status before completing proper wildcard validation with NSEC records and eventually treating the CNAME wrapper answer as bogus. The updated poisoned rrset is now secure and points to the wildcard. This vulnerability is explicit for the serve expired path and needs injection of the signed wildcard rrset without the NSEC accompanying rrset.(CVE-2026-46582)\n\nIn NLnet Labs Unbound 1.6.2 up to and including 1.25.1, when Unbound is configured with the \u0026apos;respip\u0026apos; module in front of the validator together with a \u0026apos;response-ip\u0026apos; redirect rule or an RPZ file with an RPZ-IP trigger, the rewriting handler does not check the security status of the upstream answer and can instead rewrite a BOGUS A/AAAA answer to point to an operator\u0026apos;s configured IP. If the validator finds an expired or otherwise invalid RRSIG on an answer whose A record falls within a \u0026apos;response-ip\u0026apos;/RPZ configuration, the answer is still rewritten and given a hard coded security level of INSECURE. This results in the client receiving an INSECURE NOERROR reply rewritten by the operator\u0026apos;s configured IP. A malicious actor can exploit the possible poisonous effect by spoofing a BOGUS A/AAAA answer that falls inside the operator\u0026apos;s configured subnet rewrites. Such DNSSEC protected answers are then insecurely redirected to the operator\u0026apos;s configured target.(CVE-2026-50243)\n\nIn NLnet Labs Unbound 1.7.0 up to and including 1.25.1, when an auth/rpz zone has a configured primary hostname that resolves to BOGUS A/AAAA, it is still considered as a possible XFR endpoint. A malicious actor that can spoof the hostname\u0026apos;s A/AAAA record (no valid RRSIG required) becomes the zone\u0026apos;s XFR primary and can replaces the entire zone/the resolver\u0026apos;s entire response policy.(CVE-2026-50248)\n\nIn NLnet Labs Unbound up to and including version 1.25.1, when \u0026apos;unwanted-reply-threshold\u0026apos; is enabled (set to any value greater than zero), glue records of 0.0.0.0/::0 can short-circuit Unbound, on systems that can direct such traffic, by issuing DNS queries and receiving seemingly unwanted replies since the remote IP does not match the original source IP of 0.0.0.0/::0. This behavior keeps on looping for the glue records and pushing the counter to the configured \u0026apos;unwanted-reply-threshold\u0026apos; that triggers a defensive cache clear. A malicious actor who controls a delegation that returns in-bailiwick glue of 0.0.0.0/::0 can drive the counter to the limit of \u0026apos;unwanted-reply-threshold\u0026apos; to the threshold and trigger a cache clean of the message and rrset caches; at will, indefinitely, without sending a single spoofed packet. The iterator uses the 0.0.0.0/::0 glue, and a system that can route this (e.g., Linux kernel routes the datagram over loopback), Unbound\u0026apos;s own listener answers from 127.0.0.1. Because of the mismatch of 0.0.0.0 and 127.0.0.1, in this example, Unbound accounts the reply as an unwanted (probably spoofed) answer. The counter resets to zero on every cache flush, so the attack loops forever.(CVE-2026-50251)\n\nIn NLnet Labs Unbound 1.6.0 up to and including 1.25.1, the \u0026apos;view_local_data\u0026apos; and \u0026apos;view_local_datas\u0026apos; commands of \u0026apos;unbound-control\u0026apos; create a bare local zones tree for an already configured named view when the view is configured with no local data to begin with. However, the creation through the control interface omits adding the default-protected zones (e.g., RFC 1918 reverse, AS112 zones, .onion, .localhost). Once the local zone tree exists without the defaults, every query for a default-protected name from a client mapped to that view escapes to the public DNS via the iterator instead of being answered locally, bypassing local policy expectations.(CVE-2026-55708)\n\nIn NLnet Labs Unbound 1.10.0 up to and including 1.25.1, when \u0026apos;serve-expired: yes\u0026apos; is set together with a \u0026apos;response-ip: \u0026lt;net\u0026gt; redirect\u0026apos; /\u0026apos;response-ip-data: \u0026lt;net\u0026gt; CNAME \u0026lt;target\u0026gt;\u0026apos; rule (or the RPZ \u0026apos;rpz-cname-override\u0026apos; equivalent), a remote client who controls any delegated domain can crash the daemon. The serve-expired-client-timeout callback runs a two-pass loop to chase the respip-generated CNAME alias; on the second pass it resets \u0026apos;alias_rrset\u0026apos; but not \u0026apos;partial_rep\u0026apos;. Later, this inconsistency leads to a NULL pointer dereference and an eventual crash. A malicious actor can exploit the vulnerability by controlling any zone that replies with an A/AAAA record that falls inside the configured response-ip/rpz subnet. By delaying the answer when the previous record has expired, the vulnerable path of \u0026apos;serve-expired-client-timeout\u0026apos; is taken leading to denial of service via the server crash.(CVE-2026-55717)\n\nIn NLnet Labs Unbound 1.7.0 up to and including 1.25.1, when the \u0026apos;dnscrypt:\u0026apos; clause lists more \u0026apos;dnscrypt-provider-cert:\u0026apos; files than there are matching \u0026apos;dnscrypt-secret-key:\u0026apos; files, Unbound fills only the matched prefix and leaves the tail slots at the \u0026apos;0xdb\u0026apos; fill that libsodium\u0026apos;s allocator writes into every allocation. Unbound would then iterate over the number of cert files, not the actual slots, so it walks into a slot with garbage data filled with \u0026apos;0xdb\u0026apos; bytes. Any unauthenticated client that sends one UDP datagram of \u2265 68 bytes whose first 8 bytes are \u0026apos;0xdb\u0026apos; to \u0026apos;dnscrypt-port\u0026apos; will use that garbage entry which leads to a garbage dereference killing the server. This is a silent faulty configuration that goes unnoticed until triggered with the right client query. Unbound needs to be compiled with DNSCrypt support (\u0026apos;--enable-dnscrypt\u0026apos;).(CVE-2026-55990)\n\nIn NLnet Labs Unbound up to and including version 1.25.1, when the validator builds the canonical RDATA form for an RRSIG-covered PX/RP/MINFO/SOA RRset, it computes the address of the second embedded domain name as \u0026apos;datstart + dname_valid(datstart, ...)\u0026apos; and passes it straight to \u0026apos;query_dname_tolower()\u0026apos; without checking that a second name is actually present in the RDATA. The wire-format parser accepts multi-dname RRs whose RDATA ends after the first name, so an attacker who runs a DNSSEC-signed authoritative server can deliver a record with an absent second domain name (e.g. SOA record) and cause \u0026apos;query_dname_tolower()\u0026apos; to walk label-by-label through stale bytes in the per-worker \u0026apos;env-\u0026gt;scratch_buffer\u0026apos;, past the end of that heap allocation if \u0026apos;msg-buffer-size\u0026apos; has been lowered from the default. This leads to heap buffer overflow and on a release build the outcome relies heavily on the contents of the buffer tail and the adjacent heap chunk.(CVE-2026-56416)",
  "id": "OESA-2026-3333",
  "modified": "2026-08-13T13:59:28Z",
  "published": "2026-08-13T13:59:28Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://www.openeuler.org/zh/security/security-bulletins/detail/?id=openEuler-SA-2026-3333"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-44621"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-44690"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-46582"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-50243"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-50248"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-50251"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-55708"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-55717"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-55990"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-56416"
    }
  ],
  "schema_version": "1.7.2",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "unbound security update",
  "upstream": [
    "CVE-2026-44621",
    "CVE-2026-44690",
    "CVE-2026-46582",
    "CVE-2026-50243",
    "CVE-2026-50248",
    "CVE-2026-50251",
    "CVE-2026-55708",
    "CVE-2026-55717",
    "CVE-2026-55990",
    "CVE-2026-56416"
  ]
}

{
  "affected": [
    {
      "ecosystem_specific": {
        "aarch64": [
          "python3-unbound-1.17.1-19.oe2403sp1.aarch64.rpm",
          "unbound-1.17.1-19.oe2403sp1.aarch64.rpm",
          "unbound-anchor-1.17.1-19.oe2403sp1.aarch64.rpm",
          "unbound-debuginfo-1.17.1-19.oe2403sp1.aarch64.rpm",
          "unbound-debugsource-1.17.1-19.oe2403sp1.aarch64.rpm",
          "unbound-devel-1.17.1-19.oe2403sp1.aarch64.rpm",
          "unbound-help-1.17.1-19.oe2403sp1.aarch64.rpm",
          "unbound-libs-1.17.1-19.oe2403sp1.aarch64.rpm",
          "unbound-utils-1.17.1-19.oe2403sp1.aarch64.rpm"
        ],
        "src": [
          "unbound-1.17.1-19.oe2403sp1.src.rpm"
        ],
        "x86_64": [
          "python3-unbound-1.17.1-19.oe2403sp1.x86_64.rpm",
          "unbound-1.17.1-19.oe2403sp1.x86_64.rpm",
          "unbound-anchor-1.17.1-19.oe2403sp1.x86_64.rpm",
          "unbound-debuginfo-1.17.1-19.oe2403sp1.x86_64.rpm",
          "unbound-debugsource-1.17.1-19.oe2403sp1.x86_64.rpm",
          "unbound-devel-1.17.1-19.oe2403sp1.x86_64.rpm",
          "unbound-help-1.17.1-19.oe2403sp1.x86_64.rpm",
          "unbound-libs-1.17.1-19.oe2403sp1.x86_64.rpm",
          "unbound-utils-1.17.1-19.oe2403sp1.x86_64.rpm"
        ]
      },
      "package": {
        "ecosystem": "openEuler:24.03-LTS-SP1",
        "name": "unbound",
        "purl": "pkg:rpm/openEuler/unbound\u0026distro=openEuler-24.03-LTS-SP1"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "1.17.1-19.oe2403sp1"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "database_specific": {
    "severity": "High"
  },
  "details": "Unbound is a validating, recursive, caching DNS resolver. It is designed to be fast and lean and incorporates modern features based on open standards. To help increase online privacy, Unbound supports DNS-over-TLS which allows clients to encrypt their communication. Unbound is available for most platforms such as FreeBSD, OpenBSD, NetBSD, MacOS, Linux and Microsoft Windows. Unbound is a totally free, open source software under the BSD license. It doesn\u0026amp;apos;t make custom builds or provide specific features to paying customers only.\r\n\r\nSecurity Fix(es):\n\nIn Unbound 1.9.0 up to and including 1.25.1, when a DNSCrypt query is received over TCP, the routine that encrypts the reply in place fails to bound the reply length against the destination buffer size. The size clamp that protects the UDP path is not applied on the TCP path, so a reply larger than 65504 bytes is shifted forward by 48 bytes inside a buffer of capacity equal to \u0026apos;msg-buffer-size\u0026apos;, writing past the end of the heap allocation. A single malicious encrypted query crashes the resolver and lead to denial of service. This vulnerability needs Unbound to be compiled with DNSCrypt support (\u0026apos;--enable-dnscrypt\u0026apos;) and the \u0026apos;dnscrypt:\u0026apos; clause to be configured and enabled for the listening interfaces.(CVE-2026-40691)\n\nWith NLnet Labs Unbound up to and including version 1.25.1, applications using libunbound and configured with \u0026apos;unwanted-reply-threshold\u0026apos;, could eventually be abruptly terminated if the threshold is reached and libunbound needs to call \u0026apos;libworker_alloc_cleanup\u0026apos; since the function is absent from the function call allow list. When an application using libunbound sets \u0026apos;unwanted-reply-threshold\u0026apos; to any non-zero value and the iterator queries an authoritative that replies with enough wrong-transaction-ID UDP datagrams to cross the threshold, the \u0026apos;libworker_alloc_cleanup\u0026apos; will eventually be called. Since the function is absent from the function call allow list, this leads to a fatal exit of libunbound and eventual termination of the embedding application.Unbound itself is not affected since its relevant function \u0026apos;worker_alloc_cleanup\u0026apos; is registed in the allow list and proceeds to perform the documented cache flush.(CVE-2026-44621)\n\nIn NLnet Labs Unbound 1.7.0 up to and including 1.25.1, insufficient validation of the RRSIG.Labels field combined with premature cache writes during RFC 8198 aggressive NSEC processing leads to cache poisoning that permits a malicious actor controlling a single delegated zone to poison arbitrary sibling zones under NSEC-signed parent domains. A malicious actor with one registered domain under an NSEC-signed TLD can serve malicious insecure DNS responses for unrelated sibling domains (sharing the same parent zone). Arbitrary delegations that do not exist under the parent domain and are covered by the parent\u0026apos;s NSEC chain can be brought into insecure existence by fraudulent wildcard DS records (less labels than expected, unknown algorithm) from the malicious sibling domain. This allows the malicious actor to inject insecure wildcard records for those delegations.(CVE-2026-44690)\n\nIn NLnet Labs Unbound 1.6.0 up to and including 1.25.1, a replay of a wildcard rrset as another piece of data, could be briefly considered DNSSEC secure based only on the RRSIG validation and stored into cache, before later validation treats it as bogus based on NSEC validation. When the resolving thread puts secure on the rrset, and another thread that is on the serve expired path then picks up the updated rrset contents with the secure status for a reply, it can be used to change a specific record, next to a wildcard that could be covered by the wildcard, into the wildcard. A malicious actor can exploit the possible poisonous effect by having any DNSSEC-singed domain (irrelevant to the victim domain) and a CNAME wrapper record that points to a record next to a wildcard (that could be covered by the wildcard). Then quering Unbound for the wildcard sibling record would seed the secure message. A later (after expiry) query for the CNAME wrapper would need to resolve the target sibling record. If the wildcard replay is injected into the response, the wildcard rrset will update the expired sibling record with a secure status before completing proper wildcard validation with NSEC records and eventually treating the CNAME wrapper answer as bogus. The updated poisoned rrset is now secure and points to the wildcard. This vulnerability is explicit for the serve expired path and needs injection of the signed wildcard rrset without the NSEC accompanying rrset.(CVE-2026-46582)\n\nIn NLnet Labs Unbound 1.6.2 up to and including 1.25.1, when Unbound is configured with the \u0026apos;respip\u0026apos; module in front of the validator together with a \u0026apos;response-ip\u0026apos; redirect rule or an RPZ file with an RPZ-IP trigger, the rewriting handler does not check the security status of the upstream answer and can instead rewrite a BOGUS A/AAAA answer to point to an operator\u0026apos;s configured IP. If the validator finds an expired or otherwise invalid RRSIG on an answer whose A record falls within a \u0026apos;response-ip\u0026apos;/RPZ configuration, the answer is still rewritten and given a hard coded security level of INSECURE. This results in the client receiving an INSECURE NOERROR reply rewritten by the operator\u0026apos;s configured IP. A malicious actor can exploit the possible poisonous effect by spoofing a BOGUS A/AAAA answer that falls inside the operator\u0026apos;s configured subnet rewrites. Such DNSSEC protected answers are then insecurely redirected to the operator\u0026apos;s configured target.(CVE-2026-50243)\n\nIn NLnet Labs Unbound 1.7.0 up to and including 1.25.1, when an auth/rpz zone has a configured primary hostname that resolves to BOGUS A/AAAA, it is still considered as a possible XFR endpoint. A malicious actor that can spoof the hostname\u0026apos;s A/AAAA record (no valid RRSIG required) becomes the zone\u0026apos;s XFR primary and can replaces the entire zone/the resolver\u0026apos;s entire response policy.(CVE-2026-50248)\n\nIn NLnet Labs Unbound up to and including version 1.25.1, when \u0026apos;unwanted-reply-threshold\u0026apos; is enabled (set to any value greater than zero), glue records of 0.0.0.0/::0 can short-circuit Unbound, on systems that can direct such traffic, by issuing DNS queries and receiving seemingly unwanted replies since the remote IP does not match the original source IP of 0.0.0.0/::0. This behavior keeps on looping for the glue records and pushing the counter to the configured \u0026apos;unwanted-reply-threshold\u0026apos; that triggers a defensive cache clear. A malicious actor who controls a delegation that returns in-bailiwick glue of 0.0.0.0/::0 can drive the counter to the limit of \u0026apos;unwanted-reply-threshold\u0026apos; to the threshold and trigger a cache clean of the message and rrset caches; at will, indefinitely, without sending a single spoofed packet. The iterator uses the 0.0.0.0/::0 glue, and a system that can route this (e.g., Linux kernel routes the datagram over loopback), Unbound\u0026apos;s own listener answers from 127.0.0.1. Because of the mismatch of 0.0.0.0 and 127.0.0.1, in this example, Unbound accounts the reply as an unwanted (probably spoofed) answer. The counter resets to zero on every cache flush, so the attack loops forever.(CVE-2026-50251)\n\nIn NLnet Labs Unbound 1.6.0 up to and including 1.25.1, the \u0026apos;view_local_data\u0026apos; and \u0026apos;view_local_datas\u0026apos; commands of \u0026apos;unbound-control\u0026apos; create a bare local zones tree for an already configured named view when the view is configured with no local data to begin with. However, the creation through the control interface omits adding the default-protected zones (e.g., RFC 1918 reverse, AS112 zones, .onion, .localhost). Once the local zone tree exists without the defaults, every query for a default-protected name from a client mapped to that view escapes to the public DNS via the iterator instead of being answered locally, bypassing local policy expectations.(CVE-2026-55708)\n\nIn NLnet Labs Unbound 1.10.0 up to and including 1.25.1, when \u0026apos;serve-expired: yes\u0026apos; is set together with a \u0026apos;response-ip: \u0026lt;net\u0026gt; redirect\u0026apos; /\u0026apos;response-ip-data: \u0026lt;net\u0026gt; CNAME \u0026lt;target\u0026gt;\u0026apos; rule (or the RPZ \u0026apos;rpz-cname-override\u0026apos; equivalent), a remote client who controls any delegated domain can crash the daemon. The serve-expired-client-timeout callback runs a two-pass loop to chase the respip-generated CNAME alias; on the second pass it resets \u0026apos;alias_rrset\u0026apos; but not \u0026apos;partial_rep\u0026apos;. Later, this inconsistency leads to a NULL pointer dereference and an eventual crash. A malicious actor can exploit the vulnerability by controlling any zone that replies with an A/AAAA record that falls inside the configured response-ip/rpz subnet. By delaying the answer when the previous record has expired, the vulnerable path of \u0026apos;serve-expired-client-timeout\u0026apos; is taken leading to denial of service via the server crash.(CVE-2026-55717)\n\nIn NLnet Labs Unbound 1.7.0 up to and including 1.25.1, when the \u0026apos;dnscrypt:\u0026apos; clause lists more \u0026apos;dnscrypt-provider-cert:\u0026apos; files than there are matching \u0026apos;dnscrypt-secret-key:\u0026apos; files, Unbound fills only the matched prefix and leaves the tail slots at the \u0026apos;0xdb\u0026apos; fill that libsodium\u0026apos;s allocator writes into every allocation. Unbound would then iterate over the number of cert files, not the actual slots, so it walks into a slot with garbage data filled with \u0026apos;0xdb\u0026apos; bytes. Any unauthenticated client that sends one UDP datagram of \u2265 68 bytes whose first 8 bytes are \u0026apos;0xdb\u0026apos; to \u0026apos;dnscrypt-port\u0026apos; will use that garbage entry which leads to a garbage dereference killing the server. This is a silent faulty configuration that goes unnoticed until triggered with the right client query. Unbound needs to be compiled with DNSCrypt support (\u0026apos;--enable-dnscrypt\u0026apos;).(CVE-2026-55990)\n\nIn NLnet Labs Unbound up to and including version 1.25.1, when the validator builds the canonical RDATA form for an RRSIG-covered PX/RP/MINFO/SOA RRset, it computes the address of the second embedded domain name as \u0026apos;datstart + dname_valid(datstart, ...)\u0026apos; and passes it straight to \u0026apos;query_dname_tolower()\u0026apos; without checking that a second name is actually present in the RDATA. The wire-format parser accepts multi-dname RRs whose RDATA ends after the first name, so an attacker who runs a DNSSEC-signed authoritative server can deliver a record with an absent second domain name (e.g. SOA record) and cause \u0026apos;query_dname_tolower()\u0026apos; to walk label-by-label through stale bytes in the per-worker \u0026apos;env-\u0026gt;scratch_buffer\u0026apos;, past the end of that heap allocation if \u0026apos;msg-buffer-size\u0026apos; has been lowered from the default. This leads to heap buffer overflow and on a release build the outcome relies heavily on the contents of the buffer tail and the adjacent heap chunk.(CVE-2026-56416)",
  "id": "OESA-2026-3334",
  "modified": "2026-08-13T13:59:37Z",
  "published": "2026-08-13T13:59:37Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://www.openeuler.org/zh/security/security-bulletins/detail/?id=openEuler-SA-2026-3334"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-40691"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-44621"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-44690"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-46582"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-50243"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-50248"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-50251"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-55708"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-55717"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-55990"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-56416"
    }
  ],
  "schema_version": "1.7.2",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
      "type": "CVSS_V3"
    }
  ],
  "summary": "unbound security update",
  "upstream": [
    "CVE-2026-40691",
    "CVE-2026-44621",
    "CVE-2026-44690",
    "CVE-2026-46582",
    "CVE-2026-50243",
    "CVE-2026-50248",
    "CVE-2026-50251",
    "CVE-2026-55708",
    "CVE-2026-55717",
    "CVE-2026-55990",
    "CVE-2026-56416"
  ]
}

{
  "affected": [
    {
      "ecosystem_specific": {
        "aarch64": [
          "python3-unbound-1.17.1-19.oe2403sp3.aarch64.rpm",
          "unbound-1.17.1-19.oe2403sp3.aarch64.rpm",
          "unbound-anchor-1.17.1-19.oe2403sp3.aarch64.rpm",
          "unbound-debuginfo-1.17.1-19.oe2403sp3.aarch64.rpm",
          "unbound-debugsource-1.17.1-19.oe2403sp3.aarch64.rpm",
          "unbound-devel-1.17.1-19.oe2403sp3.aarch64.rpm",
          "unbound-help-1.17.1-19.oe2403sp3.aarch64.rpm",
          "unbound-libs-1.17.1-19.oe2403sp3.aarch64.rpm",
          "unbound-utils-1.17.1-19.oe2403sp3.aarch64.rpm"
        ],
        "src": [
          "unbound-1.17.1-19.oe2403sp3.src.rpm"
        ],
        "x86_64": [
          "python3-unbound-1.17.1-19.oe2403sp3.x86_64.rpm",
          "unbound-1.17.1-19.oe2403sp3.x86_64.rpm",
          "unbound-anchor-1.17.1-19.oe2403sp3.x86_64.rpm",
          "unbound-debuginfo-1.17.1-19.oe2403sp3.x86_64.rpm",
          "unbound-debugsource-1.17.1-19.oe2403sp3.x86_64.rpm",
          "unbound-devel-1.17.1-19.oe2403sp3.x86_64.rpm",
          "unbound-help-1.17.1-19.oe2403sp3.x86_64.rpm",
          "unbound-libs-1.17.1-19.oe2403sp3.x86_64.rpm",
          "unbound-utils-1.17.1-19.oe2403sp3.x86_64.rpm"
        ]
      },
      "package": {
        "ecosystem": "openEuler:24.03-LTS-SP3",
        "name": "unbound",
        "purl": "pkg:rpm/openEuler/unbound\u0026distro=openEuler-24.03-LTS-SP3"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "1.17.1-19.oe2403sp3"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "database_specific": {
    "severity": "High"
  },
  "details": "Unbound is a validating, recursive, caching DNS resolver. It is designed to be fast and lean and incorporates modern features based on open standards. To help increase online privacy, Unbound supports DNS-over-TLS which allows clients to encrypt their communication. Unbound is available for most platforms such as FreeBSD, OpenBSD, NetBSD, MacOS, Linux and Microsoft Windows. Unbound is a totally free, open source software under the BSD license. It doesn\u0026amp;apos;t make custom builds or provide specific features to paying customers only.\r\n\r\nSecurity Fix(es):\n\nIn Unbound 1.9.0 up to and including 1.25.1, when a DNSCrypt query is received over TCP, the routine that encrypts the reply in place fails to bound the reply length against the destination buffer size. The size clamp that protects the UDP path is not applied on the TCP path, so a reply larger than 65504 bytes is shifted forward by 48 bytes inside a buffer of capacity equal to \u0026apos;msg-buffer-size\u0026apos;, writing past the end of the heap allocation. A single malicious encrypted query crashes the resolver and lead to denial of service. This vulnerability needs Unbound to be compiled with DNSCrypt support (\u0026apos;--enable-dnscrypt\u0026apos;) and the \u0026apos;dnscrypt:\u0026apos; clause to be configured and enabled for the listening interfaces.(CVE-2026-40691)\n\nWith NLnet Labs Unbound up to and including version 1.25.1, applications using libunbound and configured with \u0026apos;unwanted-reply-threshold\u0026apos;, could eventually be abruptly terminated if the threshold is reached and libunbound needs to call \u0026apos;libworker_alloc_cleanup\u0026apos; since the function is absent from the function call allow list. When an application using libunbound sets \u0026apos;unwanted-reply-threshold\u0026apos; to any non-zero value and the iterator queries an authoritative that replies with enough wrong-transaction-ID UDP datagrams to cross the threshold, the \u0026apos;libworker_alloc_cleanup\u0026apos; will eventually be called. Since the function is absent from the function call allow list, this leads to a fatal exit of libunbound and eventual termination of the embedding application.Unbound itself is not affected since its relevant function \u0026apos;worker_alloc_cleanup\u0026apos; is registed in the allow list and proceeds to perform the documented cache flush.(CVE-2026-44621)\n\nIn NLnet Labs Unbound 1.7.0 up to and including 1.25.1, insufficient validation of the RRSIG.Labels field combined with premature cache writes during RFC 8198 aggressive NSEC processing leads to cache poisoning that permits a malicious actor controlling a single delegated zone to poison arbitrary sibling zones under NSEC-signed parent domains. A malicious actor with one registered domain under an NSEC-signed TLD can serve malicious insecure DNS responses for unrelated sibling domains (sharing the same parent zone). Arbitrary delegations that do not exist under the parent domain and are covered by the parent\u0026apos;s NSEC chain can be brought into insecure existence by fraudulent wildcard DS records (less labels than expected, unknown algorithm) from the malicious sibling domain. This allows the malicious actor to inject insecure wildcard records for those delegations.(CVE-2026-44690)\n\nIn NLnet Labs Unbound 1.6.0 up to and including 1.25.1, a replay of a wildcard rrset as another piece of data, could be briefly considered DNSSEC secure based only on the RRSIG validation and stored into cache, before later validation treats it as bogus based on NSEC validation. When the resolving thread puts secure on the rrset, and another thread that is on the serve expired path then picks up the updated rrset contents with the secure status for a reply, it can be used to change a specific record, next to a wildcard that could be covered by the wildcard, into the wildcard. A malicious actor can exploit the possible poisonous effect by having any DNSSEC-singed domain (irrelevant to the victim domain) and a CNAME wrapper record that points to a record next to a wildcard (that could be covered by the wildcard). Then quering Unbound for the wildcard sibling record would seed the secure message. A later (after expiry) query for the CNAME wrapper would need to resolve the target sibling record. If the wildcard replay is injected into the response, the wildcard rrset will update the expired sibling record with a secure status before completing proper wildcard validation with NSEC records and eventually treating the CNAME wrapper answer as bogus. The updated poisoned rrset is now secure and points to the wildcard. This vulnerability is explicit for the serve expired path and needs injection of the signed wildcard rrset without the NSEC accompanying rrset.(CVE-2026-46582)\n\nIn NLnet Labs Unbound 1.6.2 up to and including 1.25.1, when Unbound is configured with the \u0026apos;respip\u0026apos; module in front of the validator together with a \u0026apos;response-ip\u0026apos; redirect rule or an RPZ file with an RPZ-IP trigger, the rewriting handler does not check the security status of the upstream answer and can instead rewrite a BOGUS A/AAAA answer to point to an operator\u0026apos;s configured IP. If the validator finds an expired or otherwise invalid RRSIG on an answer whose A record falls within a \u0026apos;response-ip\u0026apos;/RPZ configuration, the answer is still rewritten and given a hard coded security level of INSECURE. This results in the client receiving an INSECURE NOERROR reply rewritten by the operator\u0026apos;s configured IP. A malicious actor can exploit the possible poisonous effect by spoofing a BOGUS A/AAAA answer that falls inside the operator\u0026apos;s configured subnet rewrites. Such DNSSEC protected answers are then insecurely redirected to the operator\u0026apos;s configured target.(CVE-2026-50243)\n\nIn NLnet Labs Unbound 1.7.0 up to and including 1.25.1, when an auth/rpz zone has a configured primary hostname that resolves to BOGUS A/AAAA, it is still considered as a possible XFR endpoint. A malicious actor that can spoof the hostname\u0026apos;s A/AAAA record (no valid RRSIG required) becomes the zone\u0026apos;s XFR primary and can replaces the entire zone/the resolver\u0026apos;s entire response policy.(CVE-2026-50248)\n\nIn NLnet Labs Unbound up to and including version 1.25.1, when \u0026apos;unwanted-reply-threshold\u0026apos; is enabled (set to any value greater than zero), glue records of 0.0.0.0/::0 can short-circuit Unbound, on systems that can direct such traffic, by issuing DNS queries and receiving seemingly unwanted replies since the remote IP does not match the original source IP of 0.0.0.0/::0. This behavior keeps on looping for the glue records and pushing the counter to the configured \u0026apos;unwanted-reply-threshold\u0026apos; that triggers a defensive cache clear. A malicious actor who controls a delegation that returns in-bailiwick glue of 0.0.0.0/::0 can drive the counter to the limit of \u0026apos;unwanted-reply-threshold\u0026apos; to the threshold and trigger a cache clean of the message and rrset caches; at will, indefinitely, without sending a single spoofed packet. The iterator uses the 0.0.0.0/::0 glue, and a system that can route this (e.g., Linux kernel routes the datagram over loopback), Unbound\u0026apos;s own listener answers from 127.0.0.1. Because of the mismatch of 0.0.0.0 and 127.0.0.1, in this example, Unbound accounts the reply as an unwanted (probably spoofed) answer. The counter resets to zero on every cache flush, so the attack loops forever.(CVE-2026-50251)\n\nIn NLnet Labs Unbound 1.6.0 up to and including 1.25.1, the \u0026apos;view_local_data\u0026apos; and \u0026apos;view_local_datas\u0026apos; commands of \u0026apos;unbound-control\u0026apos; create a bare local zones tree for an already configured named view when the view is configured with no local data to begin with. However, the creation through the control interface omits adding the default-protected zones (e.g., RFC 1918 reverse, AS112 zones, .onion, .localhost). Once the local zone tree exists without the defaults, every query for a default-protected name from a client mapped to that view escapes to the public DNS via the iterator instead of being answered locally, bypassing local policy expectations.(CVE-2026-55708)\n\nIn NLnet Labs Unbound 1.10.0 up to and including 1.25.1, when \u0026apos;serve-expired: yes\u0026apos; is set together with a \u0026apos;response-ip: \u0026lt;net\u0026gt; redirect\u0026apos; /\u0026apos;response-ip-data: \u0026lt;net\u0026gt; CNAME \u0026lt;target\u0026gt;\u0026apos; rule (or the RPZ \u0026apos;rpz-cname-override\u0026apos; equivalent), a remote client who controls any delegated domain can crash the daemon. The serve-expired-client-timeout callback runs a two-pass loop to chase the respip-generated CNAME alias; on the second pass it resets \u0026apos;alias_rrset\u0026apos; but not \u0026apos;partial_rep\u0026apos;. Later, this inconsistency leads to a NULL pointer dereference and an eventual crash. A malicious actor can exploit the vulnerability by controlling any zone that replies with an A/AAAA record that falls inside the configured response-ip/rpz subnet. By delaying the answer when the previous record has expired, the vulnerable path of \u0026apos;serve-expired-client-timeout\u0026apos; is taken leading to denial of service via the server crash.(CVE-2026-55717)\n\nIn NLnet Labs Unbound 1.7.0 up to and including 1.25.1, when the \u0026apos;dnscrypt:\u0026apos; clause lists more \u0026apos;dnscrypt-provider-cert:\u0026apos; files than there are matching \u0026apos;dnscrypt-secret-key:\u0026apos; files, Unbound fills only the matched prefix and leaves the tail slots at the \u0026apos;0xdb\u0026apos; fill that libsodium\u0026apos;s allocator writes into every allocation. Unbound would then iterate over the number of cert files, not the actual slots, so it walks into a slot with garbage data filled with \u0026apos;0xdb\u0026apos; bytes. Any unauthenticated client that sends one UDP datagram of \u2265 68 bytes whose first 8 bytes are \u0026apos;0xdb\u0026apos; to \u0026apos;dnscrypt-port\u0026apos; will use that garbage entry which leads to a garbage dereference killing the server. This is a silent faulty configuration that goes unnoticed until triggered with the right client query. Unbound needs to be compiled with DNSCrypt support (\u0026apos;--enable-dnscrypt\u0026apos;).(CVE-2026-55990)\n\nIn NLnet Labs Unbound up to and including version 1.25.1, when the validator builds the canonical RDATA form for an RRSIG-covered PX/RP/MINFO/SOA RRset, it computes the address of the second embedded domain name as \u0026apos;datstart + dname_valid(datstart, ...)\u0026apos; and passes it straight to \u0026apos;query_dname_tolower()\u0026apos; without checking that a second name is actually present in the RDATA. The wire-format parser accepts multi-dname RRs whose RDATA ends after the first name, so an attacker who runs a DNSSEC-signed authoritative server can deliver a record with an absent second domain name (e.g. SOA record) and cause \u0026apos;query_dname_tolower()\u0026apos; to walk label-by-label through stale bytes in the per-worker \u0026apos;env-\u0026gt;scratch_buffer\u0026apos;, past the end of that heap allocation if \u0026apos;msg-buffer-size\u0026apos; has been lowered from the default. This leads to heap buffer overflow and on a release build the outcome relies heavily on the contents of the buffer tail and the adjacent heap chunk.(CVE-2026-56416)",
  "id": "OESA-2026-3335",
  "modified": "2026-08-13T13:59:44Z",
  "published": "2026-08-13T13:59:44Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://www.openeuler.org/zh/security/security-bulletins/detail/?id=openEuler-SA-2026-3335"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-40691"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-44621"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-44690"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-46582"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-50243"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-50248"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-50251"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-55708"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-55717"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-55990"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-56416"
    }
  ],
  "schema_version": "1.7.2",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
      "type": "CVSS_V3"
    }
  ],
  "summary": "unbound security update",
  "upstream": [
    "CVE-2026-40691",
    "CVE-2026-44621",
    "CVE-2026-44690",
    "CVE-2026-46582",
    "CVE-2026-50243",
    "CVE-2026-50248",
    "CVE-2026-50251",
    "CVE-2026-55708",
    "CVE-2026-55717",
    "CVE-2026-55990",
    "CVE-2026-56416"
  ]
}

{
  "affected": [
    {
      "ecosystem_specific": {
        "aarch64": [
          "python3-unbound-1.11.0-25.oe2003sp4.aarch64.rpm",
          "unbound-1.11.0-25.oe2003sp4.aarch64.rpm",
          "unbound-debuginfo-1.11.0-25.oe2003sp4.aarch64.rpm",
          "unbound-debugsource-1.11.0-25.oe2003sp4.aarch64.rpm",
          "unbound-devel-1.11.0-25.oe2003sp4.aarch64.rpm",
          "unbound-help-1.11.0-25.oe2003sp4.aarch64.rpm",
          "unbound-libs-1.11.0-25.oe2003sp4.aarch64.rpm"
        ],
        "src": [
          "unbound-1.11.0-25.oe2003sp4.src.rpm"
        ],
        "x86_64": [
          "python3-unbound-1.11.0-25.oe2003sp4.x86_64.rpm",
          "unbound-1.11.0-25.oe2003sp4.x86_64.rpm",
          "unbound-debuginfo-1.11.0-25.oe2003sp4.x86_64.rpm",
          "unbound-debugsource-1.11.0-25.oe2003sp4.x86_64.rpm",
          "unbound-devel-1.11.0-25.oe2003sp4.x86_64.rpm",
          "unbound-help-1.11.0-25.oe2003sp4.x86_64.rpm",
          "unbound-libs-1.11.0-25.oe2003sp4.x86_64.rpm"
        ]
      },
      "package": {
        "ecosystem": "openEuler:20.03-LTS-SP4",
        "name": "unbound",
        "purl": "pkg:rpm/openEuler/unbound\u0026distro=openEuler-20.03-LTS-SP4"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "1.11.0-25.oe2003sp4"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "database_specific": {
    "severity": "High"
  },
  "details": "Unbound is a validating, recursive, caching DNS resolver. It is designed to be fast and lean and incorporates modern features based on open standards. To help increase online privacy, Unbound supports DNS-over-TLS which allows clients to encrypt their communication. Unbound is available for most platforms such as FreeBSD, OpenBSD, NetBSD, MacOS, Linux and Microsoft Windows. Unbound is a totally free, open source software under the BSD license. It doesn\u0026amp;apos;t make custom builds or provide specific features to paying customers only.\r\n\r\nSecurity Fix(es):\n\nWith NLnet Labs Unbound up to and including version 1.25.1, applications using libunbound and configured with \u0026apos;unwanted-reply-threshold\u0026apos;, could eventually be abruptly terminated if the threshold is reached and libunbound needs to call \u0026apos;libworker_alloc_cleanup\u0026apos; since the function is absent from the function call allow list. When an application using libunbound sets \u0026apos;unwanted-reply-threshold\u0026apos; to any non-zero value and the iterator queries an authoritative that replies with enough wrong-transaction-ID UDP datagrams to cross the threshold, the \u0026apos;libworker_alloc_cleanup\u0026apos; will eventually be called. Since the function is absent from the function call allow list, this leads to a fatal exit of libunbound and eventual termination of the embedding application.Unbound itself is not affected since its relevant function \u0026apos;worker_alloc_cleanup\u0026apos; is registed in the allow list and proceeds to perform the documented cache flush.(CVE-2026-44621)\n\nIn NLnet Labs Unbound 1.7.0 up to and including 1.25.1, insufficient validation of the RRSIG.Labels field combined with premature cache writes during RFC 8198 aggressive NSEC processing leads to cache poisoning that permits a malicious actor controlling a single delegated zone to poison arbitrary sibling zones under NSEC-signed parent domains. A malicious actor with one registered domain under an NSEC-signed TLD can serve malicious insecure DNS responses for unrelated sibling domains (sharing the same parent zone). Arbitrary delegations that do not exist under the parent domain and are covered by the parent\u0026apos;s NSEC chain can be brought into insecure existence by fraudulent wildcard DS records (less labels than expected, unknown algorithm) from the malicious sibling domain. This allows the malicious actor to inject insecure wildcard records for those delegations.(CVE-2026-44690)\n\nIn NLnet Labs Unbound 1.6.0 up to and including 1.25.1, a replay of a wildcard rrset as another piece of data, could be briefly considered DNSSEC secure based only on the RRSIG validation and stored into cache, before later validation treats it as bogus based on NSEC validation. When the resolving thread puts secure on the rrset, and another thread that is on the serve expired path then picks up the updated rrset contents with the secure status for a reply, it can be used to change a specific record, next to a wildcard that could be covered by the wildcard, into the wildcard. A malicious actor can exploit the possible poisonous effect by having any DNSSEC-singed domain (irrelevant to the victim domain) and a CNAME wrapper record that points to a record next to a wildcard (that could be covered by the wildcard). Then quering Unbound for the wildcard sibling record would seed the secure message. A later (after expiry) query for the CNAME wrapper would need to resolve the target sibling record. If the wildcard replay is injected into the response, the wildcard rrset will update the expired sibling record with a secure status before completing proper wildcard validation with NSEC records and eventually treating the CNAME wrapper answer as bogus. The updated poisoned rrset is now secure and points to the wildcard. This vulnerability is explicit for the serve expired path and needs injection of the signed wildcard rrset without the NSEC accompanying rrset.(CVE-2026-46582)\n\nIn NLnet Labs Unbound 1.6.2 up to and including 1.25.1, when Unbound is configured with the \u0026apos;respip\u0026apos; module in front of the validator together with a \u0026apos;response-ip\u0026apos; redirect rule or an RPZ file with an RPZ-IP trigger, the rewriting handler does not check the security status of the upstream answer and can instead rewrite a BOGUS A/AAAA answer to point to an operator\u0026apos;s configured IP. If the validator finds an expired or otherwise invalid RRSIG on an answer whose A record falls within a \u0026apos;response-ip\u0026apos;/RPZ configuration, the answer is still rewritten and given a hard coded security level of INSECURE. This results in the client receiving an INSECURE NOERROR reply rewritten by the operator\u0026apos;s configured IP. A malicious actor can exploit the possible poisonous effect by spoofing a BOGUS A/AAAA answer that falls inside the operator\u0026apos;s configured subnet rewrites. Such DNSSEC protected answers are then insecurely redirected to the operator\u0026apos;s configured target.(CVE-2026-50243)\n\nIn NLnet Labs Unbound 1.7.0 up to and including 1.25.1, when an auth/rpz zone has a configured primary hostname that resolves to BOGUS A/AAAA, it is still considered as a possible XFR endpoint. A malicious actor that can spoof the hostname\u0026apos;s A/AAAA record (no valid RRSIG required) becomes the zone\u0026apos;s XFR primary and can replaces the entire zone/the resolver\u0026apos;s entire response policy.(CVE-2026-50248)\n\nIn NLnet Labs Unbound up to and including version 1.25.1, when \u0026apos;unwanted-reply-threshold\u0026apos; is enabled (set to any value greater than zero), glue records of 0.0.0.0/::0 can short-circuit Unbound, on systems that can direct such traffic, by issuing DNS queries and receiving seemingly unwanted replies since the remote IP does not match the original source IP of 0.0.0.0/::0. This behavior keeps on looping for the glue records and pushing the counter to the configured \u0026apos;unwanted-reply-threshold\u0026apos; that triggers a defensive cache clear. A malicious actor who controls a delegation that returns in-bailiwick glue of 0.0.0.0/::0 can drive the counter to the limit of \u0026apos;unwanted-reply-threshold\u0026apos; to the threshold and trigger a cache clean of the message and rrset caches; at will, indefinitely, without sending a single spoofed packet. The iterator uses the 0.0.0.0/::0 glue, and a system that can route this (e.g., Linux kernel routes the datagram over loopback), Unbound\u0026apos;s own listener answers from 127.0.0.1. Because of the mismatch of 0.0.0.0 and 127.0.0.1, in this example, Unbound accounts the reply as an unwanted (probably spoofed) answer. The counter resets to zero on every cache flush, so the attack loops forever.(CVE-2026-50251)\n\nIn NLnet Labs Unbound 1.6.0 up to and including 1.25.1, the \u0026apos;view_local_data\u0026apos; and \u0026apos;view_local_datas\u0026apos; commands of \u0026apos;unbound-control\u0026apos; create a bare local zones tree for an already configured named view when the view is configured with no local data to begin with. However, the creation through the control interface omits adding the default-protected zones (e.g., RFC 1918 reverse, AS112 zones, .onion, .localhost). Once the local zone tree exists without the defaults, every query for a default-protected name from a client mapped to that view escapes to the public DNS via the iterator instead of being answered locally, bypassing local policy expectations.(CVE-2026-55708)\n\nIn NLnet Labs Unbound 1.10.0 up to and including 1.25.1, when \u0026apos;serve-expired: yes\u0026apos; is set together with a \u0026apos;response-ip: \u0026lt;net\u0026gt; redirect\u0026apos; /\u0026apos;response-ip-data: \u0026lt;net\u0026gt; CNAME \u0026lt;target\u0026gt;\u0026apos; rule (or the RPZ \u0026apos;rpz-cname-override\u0026apos; equivalent), a remote client who controls any delegated domain can crash the daemon. The serve-expired-client-timeout callback runs a two-pass loop to chase the respip-generated CNAME alias; on the second pass it resets \u0026apos;alias_rrset\u0026apos; but not \u0026apos;partial_rep\u0026apos;. Later, this inconsistency leads to a NULL pointer dereference and an eventual crash. A malicious actor can exploit the vulnerability by controlling any zone that replies with an A/AAAA record that falls inside the configured response-ip/rpz subnet. By delaying the answer when the previous record has expired, the vulnerable path of \u0026apos;serve-expired-client-timeout\u0026apos; is taken leading to denial of service via the server crash.(CVE-2026-55717)\n\nIn NLnet Labs Unbound 1.7.0 up to and including 1.25.1, when the \u0026apos;dnscrypt:\u0026apos; clause lists more \u0026apos;dnscrypt-provider-cert:\u0026apos; files than there are matching \u0026apos;dnscrypt-secret-key:\u0026apos; files, Unbound fills only the matched prefix and leaves the tail slots at the \u0026apos;0xdb\u0026apos; fill that libsodium\u0026apos;s allocator writes into every allocation. Unbound would then iterate over the number of cert files, not the actual slots, so it walks into a slot with garbage data filled with \u0026apos;0xdb\u0026apos; bytes. Any unauthenticated client that sends one UDP datagram of \u2265 68 bytes whose first 8 bytes are \u0026apos;0xdb\u0026apos; to \u0026apos;dnscrypt-port\u0026apos; will use that garbage entry which leads to a garbage dereference killing the server. This is a silent faulty configuration that goes unnoticed until triggered with the right client query. Unbound needs to be compiled with DNSCrypt support (\u0026apos;--enable-dnscrypt\u0026apos;).(CVE-2026-55990)\n\nIn NLnet Labs Unbound up to and including version 1.25.1, when the validator builds the canonical RDATA form for an RRSIG-covered PX/RP/MINFO/SOA RRset, it computes the address of the second embedded domain name as \u0026apos;datstart + dname_valid(datstart, ...)\u0026apos; and passes it straight to \u0026apos;query_dname_tolower()\u0026apos; without checking that a second name is actually present in the RDATA. The wire-format parser accepts multi-dname RRs whose RDATA ends after the first name, so an attacker who runs a DNSSEC-signed authoritative server can deliver a record with an absent second domain name (e.g. SOA record) and cause \u0026apos;query_dname_tolower()\u0026apos; to walk label-by-label through stale bytes in the per-worker \u0026apos;env-\u0026gt;scratch_buffer\u0026apos;, past the end of that heap allocation if \u0026apos;msg-buffer-size\u0026apos; has been lowered from the default. This leads to heap buffer overflow and on a release build the outcome relies heavily on the contents of the buffer tail and the adjacent heap chunk.(CVE-2026-56416)",
  "id": "OESA-2026-3336",
  "modified": "2026-08-13T13:59:51Z",
  "published": "2026-08-13T13:59:51Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://www.openeuler.org/zh/security/security-bulletins/detail/?id=openEuler-SA-2026-3336"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-44621"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-44690"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-46582"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-50243"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-50248"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-50251"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-55708"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-55717"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-55990"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-56416"
    }
  ],
  "schema_version": "1.7.2",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "unbound security update",
  "upstream": [
    "CVE-2026-44621",
    "CVE-2026-44690",
    "CVE-2026-46582",
    "CVE-2026-50243",
    "CVE-2026-50248",
    "CVE-2026-50251",
    "CVE-2026-55708",
    "CVE-2026-55717",
    "CVE-2026-55990",
    "CVE-2026-56416"
  ]
}

{
  "affected": [
    {
      "ecosystem_specific": {
        "aarch64": [
          "python3-unbound-1.17.1-20.oe2403sp4.aarch64.rpm",
          "unbound-1.17.1-20.oe2403sp4.aarch64.rpm",
          "unbound-anchor-1.17.1-20.oe2403sp4.aarch64.rpm",
          "unbound-debuginfo-1.17.1-20.oe2403sp4.aarch64.rpm",
          "unbound-debugsource-1.17.1-20.oe2403sp4.aarch64.rpm",
          "unbound-devel-1.17.1-20.oe2403sp4.aarch64.rpm",
          "unbound-help-1.17.1-20.oe2403sp4.aarch64.rpm",
          "unbound-libs-1.17.1-20.oe2403sp4.aarch64.rpm",
          "unbound-utils-1.17.1-20.oe2403sp4.aarch64.rpm"
        ],
        "src": [
          "unbound-1.17.1-20.oe2403sp4.src.rpm"
        ],
        "x86_64": [
          "python3-unbound-1.17.1-20.oe2403sp4.x86_64.rpm",
          "unbound-1.17.1-20.oe2403sp4.x86_64.rpm",
          "unbound-anchor-1.17.1-20.oe2403sp4.x86_64.rpm",
          "unbound-debuginfo-1.17.1-20.oe2403sp4.x86_64.rpm",
          "unbound-debugsource-1.17.1-20.oe2403sp4.x86_64.rpm",
          "unbound-devel-1.17.1-20.oe2403sp4.x86_64.rpm",
          "unbound-help-1.17.1-20.oe2403sp4.x86_64.rpm",
          "unbound-libs-1.17.1-20.oe2403sp4.x86_64.rpm",
          "unbound-utils-1.17.1-20.oe2403sp4.x86_64.rpm"
        ]
      },
      "package": {
        "ecosystem": "openEuler:24.03-LTS-SP4",
        "name": "unbound",
        "purl": "pkg:rpm/openEuler/unbound\u0026distro=openEuler-24.03-LTS-SP4"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "1.17.1-20.oe2403sp4"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "database_specific": {
    "severity": "High"
  },
  "details": "Unbound is a validating, recursive, caching DNS resolver. It is designed to be fast and lean and incorporates modern features based on open standards. To help increase online privacy, Unbound supports DNS-over-TLS which allows clients to encrypt their communication. Unbound is available for most platforms such as FreeBSD, OpenBSD, NetBSD, MacOS, Linux and Microsoft Windows. Unbound is a totally free, open source software under the BSD license. It doesn\u0026amp;apos;t make custom builds or provide specific features to paying customers only.\r\n\r\nSecurity Fix(es):\n\nIn Unbound 1.9.0 up to and including 1.25.1, when a DNSCrypt query is received over TCP, the routine that encrypts the reply in place fails to bound the reply length against the destination buffer size. The size clamp that protects the UDP path is not applied on the TCP path, so a reply larger than 65504 bytes is shifted forward by 48 bytes inside a buffer of capacity equal to \u0026apos;msg-buffer-size\u0026apos;, writing past the end of the heap allocation. A single malicious encrypted query crashes the resolver and lead to denial of service. This vulnerability needs Unbound to be compiled with DNSCrypt support (\u0026apos;--enable-dnscrypt\u0026apos;) and the \u0026apos;dnscrypt:\u0026apos; clause to be configured and enabled for the listening interfaces.(CVE-2026-40691)\n\nIn NLnet Labs Unbound 1.16.2 up to and including 1.25.1, a similar vulnerability as with CVE-2026-40622 in the \u0026apos;ghost domain names\u0026apos; family of attacks was found in Unbound that could extend the ghost domain window by up to one cached TTL configured value for A/AAAA glue records. Similar to other \u0026apos;ghost domain names\u0026apos; attacks, an adversary needs to control a (ghost) zone and be able to query a vulnerable Unbound. A single client A/AAAA query can cause Unbound to overwrite the cached expired parent-side glue rrset and essentially extend the ghost domain window by up to one cached TTL configured value (\u0026apos;cache-max-ttl\u0026apos;). In configurations where \u0026apos;harden-referral-path: yes\u0026apos; is used (non-default configuration), no client query is required since Unbound implicitly performs that query. This is a variant of CVE-2026-40622 which only addressed the NS query.(CVE-2026-42955)\n\nWith NLnet Labs Unbound up to and including version 1.25.1, applications using libunbound and configured with \u0026apos;unwanted-reply-threshold\u0026apos;, could eventually be abruptly terminated if the threshold is reached and libunbound needs to call \u0026apos;libworker_alloc_cleanup\u0026apos; since the function is absent from the function call allow list. When an application using libunbound sets \u0026apos;unwanted-reply-threshold\u0026apos; to any non-zero value and the iterator queries an authoritative that replies with enough wrong-transaction-ID UDP datagrams to cross the threshold, the \u0026apos;libworker_alloc_cleanup\u0026apos; will eventually be called. Since the function is absent from the function call allow list, this leads to a fatal exit of libunbound and eventual termination of the embedding application.Unbound itself is not affected since its relevant function \u0026apos;worker_alloc_cleanup\u0026apos; is registed in the allow list and proceeds to perform the documented cache flush.(CVE-2026-44621)\n\nIn NLnet Labs Unbound 1.13.2 up to and including 1.25.1, stub or forward zones where the name is below an intermediate labed below a DNSSEC signed zone could be shadowed by the intermediate label\u0026apos;s secure NXDOMAIN answer from the parent. This is caused by an off-by-one error in \u0026apos;harden-below-nxdomain\u0026apos; logic; enabled by default. It effectively bypasses the configuration and the configured stub/forward zone is never contacted. \u0026apos;harden-below-nxdomain\u0026apos; does an upward DNS cache walk together with a delegation point guard that does not allow NXDOMAIN synthesis above stub/forward zones. The guard tests the domain name but before stripping a label. This results in an iteration where the domain name equals the configured stub/forward zone apex that passes the guard, strips one more label, and probes the cache at the apex\u0026apos;s immediate public parent. If that parent has a cached DNSSEC-secure NXDOMAIN, which it will for any private namespace nested two or more labels under a signed public name, the walk returns it and the configured stub/forward upstream is never contacted. This can only be triggered by the query for the intermediate label (between the stub/forward apex and the DNSSEC parent zone).(CVE-2026-44687)\n\nIn NLnet Labs Unbound 1.7.0 up to and including 1.25.1, insufficient validation of the RRSIG.Labels field combined with premature cache writes during RFC 8198 aggressive NSEC processing leads to cache poisoning that permits a malicious actor controlling a single delegated zone to poison arbitrary sibling zones under NSEC-signed parent domains. A malicious actor with one registered domain under an NSEC-signed TLD can serve malicious insecure DNS responses for unrelated sibling domains (sharing the same parent zone). Arbitrary delegations that do not exist under the parent domain and are covered by the parent\u0026apos;s NSEC chain can be brought into insecure existence by fraudulent wildcard DS records (less labels than expected, unknown algorithm) from the malicious sibling domain. This allows the malicious actor to inject insecure wildcard records for those delegations.(CVE-2026-44690)\n\nIn NLnet Labs Unbound 1.6.0 up to and including 1.25.1, a replay of a wildcard rrset as another piece of data, could be briefly considered DNSSEC secure based only on the RRSIG validation and stored into cache, before later validation treats it as bogus based on NSEC validation. When the resolving thread puts secure on the rrset, and another thread that is on the serve expired path then picks up the updated rrset contents with the secure status for a reply, it can be used to change a specific record, next to a wildcard that could be covered by the wildcard, into the wildcard. A malicious actor can exploit the possible poisonous effect by having any DNSSEC-singed domain (irrelevant to the victim domain) and a CNAME wrapper record that points to a record next to a wildcard (that could be covered by the wildcard). Then quering Unbound for the wildcard sibling record would seed the secure message. A later (after expiry) query for the CNAME wrapper would need to resolve the target sibling record. If the wildcard replay is injected into the response, the wildcard rrset will update the expired sibling record with a secure status before completing proper wildcard validation with NSEC records and eventually treating the CNAME wrapper answer as bogus. The updated poisoned rrset is now secure and points to the wildcard. This vulnerability is explicit for the serve expired path and needs injection of the signed wildcard rrset without the NSEC accompanying rrset.(CVE-2026-46582)\n\nIn NLnet Labs Unbound 1.15.0 up to and including 1.25.1, the TLS server name used for DNS-over-TLS (DoT) forwarded queries is tied to a struct\u0026apos;s (\u0026apos;serviced_query\u0026apos;) lifetime but also referenced by another struct (\u0026apos;waiting_tcp\u0026apos;). When the owning struct is jostled out of the mesh while the DoT TCP stream is still handshaking it frees the storage behind the referenced string and if the TLS stream then errors out, it dereferences the freed pointer. The dereference is read-only and the practical impact is a daemon crash resulting in denial of service. A malicious actor that knows a DoT forwarding/stub Unbound\u0026apos;s configuration could exploit the vulnerability by quering records in the appropriate zone while keeping Unbound uder pressure so that the jostle logic kicks in. If answers for the vulnerable zone are slow, the likelihood of jostling such queries is higher, although the timing of the jostle needs to be precise. Requirements for a vulnerable Unbound is the existence of a stub/forward zone configured for DoT together with a configured \u0026apos;#authname\u0026apos; suffix on the server identification. The connectivity to the server needs to exhibit a transient failure at the correct time in order to kick off the vulnerable error path.(CVE-2026-50046)\n\nIn NLnet Labs Unbound 1.6.2 up to and including 1.25.1, when Unbound is configured with the \u0026apos;respip\u0026apos; module in front of the validator together with a \u0026apos;response-ip\u0026apos; redirect rule or an RPZ file with an RPZ-IP trigger, the rewriting handler does not check the security status of the upstream answer and can instead rewrite a BOGUS A/AAAA answer to point to an operator\u0026apos;s configured IP. If the validator finds an expired or otherwise invalid RRSIG on an answer whose A record falls within a \u0026apos;response-ip\u0026apos;/RPZ configuration, the answer is still rewritten and given a hard coded security level of INSECURE. This results in the client receiving an INSECURE NOERROR reply rewritten by the operator\u0026apos;s configured IP. A malicious actor can exploit the possible poisonous effect by spoofing a BOGUS A/AAAA answer that falls inside the operator\u0026apos;s configured subnet rewrites. Such DNSSEC protected answers are then insecurely redirected to the operator\u0026apos;s configured target.(CVE-2026-50243)\n\nIn NLnet Labs Unbound 1.7.0 up to and including 1.25.1, when an auth/rpz zone has a configured primary hostname that resolves to BOGUS A/AAAA, it is still considered as a possible XFR endpoint. A malicious actor that can spoof the hostname\u0026apos;s A/AAAA record (no valid RRSIG required) becomes the zone\u0026apos;s XFR primary and can replaces the entire zone/the resolver\u0026apos;s entire response policy.(CVE-2026-50248)\n\nIn NLnet Labs Unbound up to and including version 1.25.1, when \u0026apos;unwanted-reply-threshold\u0026apos; is enabled (set to any value greater than zero), glue records of 0.0.0.0/::0 can short-circuit Unbound, on systems that can direct such traffic, by issuing DNS queries and receiving seemingly unwanted replies since the remote IP does not match the original source IP of 0.0.0.0/::0. This behavior keeps on looping for the glue records and pushing the counter to the configured \u0026apos;unwanted-reply-threshold\u0026apos; that triggers a defensive cache clear. A malicious actor who controls a delegation that returns in-bailiwick glue of 0.0.0.0/::0 can drive the counter to the limit of \u0026apos;unwanted-reply-threshold\u0026apos; to the threshold and trigger a cache clean of the message and rrset caches; at will, indefinitely, without sending a single spoofed packet. The iterator uses the 0.0.0.0/::0 glue, and a system that can route this (e.g., Linux kernel routes the datagram over loopback), Unbound\u0026apos;s own listener answers from 127.0.0.1. Because of the mismatch of 0.0.0.0 and 127.0.0.1, in this example, Unbound accounts the reply as an unwanted (probably spoofed) answer. The counter resets to zero on every cache flush, so the attack loops forever.(CVE-2026-50251)\n\nIn NLnet Labs Unbound 1.6.0 up to and including 1.25.1, the \u0026apos;view_local_data\u0026apos; and \u0026apos;view_local_datas\u0026apos; commands of \u0026apos;unbound-control\u0026apos; create a bare local zones tree for an already configured named view when the view is configured with no local data to begin with. However, the creation through the control interface omits adding the default-protected zones (e.g., RFC 1918 reverse, AS112 zones, .onion, .localhost). Once the local zone tree exists without the defaults, every query for a default-protected name from a client mapped to that view escapes to the public DNS via the iterator instead of being answered locally, bypassing local policy expectations.(CVE-2026-55708)\n\nIn NLnet Labs Unbound 1.10.0 up to and including 1.25.1, when \u0026apos;serve-expired: yes\u0026apos; is set together with a \u0026apos;response-ip: \u0026lt;net\u0026gt; redirect\u0026apos; /\u0026apos;response-ip-data: \u0026lt;net\u0026gt; CNAME \u0026lt;target\u0026gt;\u0026apos; rule (or the RPZ \u0026apos;rpz-cname-override\u0026apos; equivalent), a remote client who controls any delegated domain can crash the daemon. The serve-expired-client-timeout callback runs a two-pass loop to chase the respip-generated CNAME alias; on the second pass it resets \u0026apos;alias_rrset\u0026apos; but not \u0026apos;partial_rep\u0026apos;. Later, this inconsistency leads to a NULL pointer dereference and an eventual crash. A malicious actor can exploit the vulnerability by controlling any zone that replies with an A/AAAA record that falls inside the configured response-ip/rpz subnet. By delaying the answer when the previous record has expired, the vulnerable path of \u0026apos;serve-expired-client-timeout\u0026apos; is taken leading to denial of service via the server crash.(CVE-2026-55717)\n\nIn NLnet Labs Unbound 1.7.0 up to and including 1.25.1, when the \u0026apos;dnscrypt:\u0026apos; clause lists more \u0026apos;dnscrypt-provider-cert:\u0026apos; files than there are matching \u0026apos;dnscrypt-secret-key:\u0026apos; files, Unbound fills only the matched prefix and leaves the tail slots at the \u0026apos;0xdb\u0026apos; fill that libsodium\u0026apos;s allocator writes into every allocation. Unbound would then iterate over the number of cert files, not the actual slots, so it walks into a slot with garbage data filled with \u0026apos;0xdb\u0026apos; bytes. Any unauthenticated client that sends one UDP datagram of \u2265 68 bytes whose first 8 bytes are \u0026apos;0xdb\u0026apos; to \u0026apos;dnscrypt-port\u0026apos; will use that garbage entry which leads to a garbage dereference killing the server. This is a silent faulty configuration that goes unnoticed until triggered with the right client query. Unbound needs to be compiled with DNSCrypt support (\u0026apos;--enable-dnscrypt\u0026apos;).(CVE-2026-55990)\n\nIn NLnet Labs Unbound up to and including version 1.25.1, when the validator builds the canonical RDATA form for an RRSIG-covered PX/RP/MINFO/SOA RRset, it computes the address of the second embedded domain name as \u0026apos;datstart + dname_valid(datstart, ...)\u0026apos; and passes it straight to \u0026apos;query_dname_tolower()\u0026apos; without checking that a second name is actually present in the RDATA. The wire-format parser accepts multi-dname RRs whose RDATA ends after the first name, so an attacker who runs a DNSSEC-signed authoritative server can deliver a record with an absent second domain name (e.g. SOA record) and cause \u0026apos;query_dname_tolower()\u0026apos; to walk label-by-label through stale bytes in the per-worker \u0026apos;env-\u0026gt;scratch_buffer\u0026apos;, past the end of that heap allocation if \u0026apos;msg-buffer-size\u0026apos; has been lowered from the default. This leads to heap buffer overflow and on a release build the outcome relies heavily on the contents of the buffer tail and the adjacent heap chunk.(CVE-2026-56416)\n\nIn NLnet Labs Unbound 1.20.0 up to and including 1.25.1, when Unbound is configured with \u0026apos;serve-expired: yes\u0026apos; and \u0026apos;serve-expired-client-timeout \u0026gt; discard-timeout \u0026gt; 0\u0026apos; (contrary to the suggested values), the discard-timeout branch during the serve expired logic drops an aged client reply without performing the correct accounting for the number of reply addresses for the query. Other identical branches outside of serve expired perform the correct decrement. Since the counter is never decremented in such scenario, it can reach the maximum limit and new clients for duplicate in-flight queries are silently dropped resulting in degradation of resolution service. A malicious actor can exploit the vulnerability by querying the resolver for a client-controlled slow-on-demand authoritative zone that can drive the counter past the threshold. Shipped defaults for \u0026apos;serve-expired-client-timeout: 1800\u0026apos; and \u0026apos;discard-timeout: 1900\u0026apos; make the branch unreachable.(CVE-2026-56444)",
  "id": "OESA-2026-3436",
  "modified": "2026-08-20T09:57:59Z",
  "published": "2026-08-20T09:57:59Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://www.openeuler.org/zh/security/security-bulletins/detail/?id=openEuler-SA-2026-3436"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-40691"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-42955"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-44621"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-44687"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-44690"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-46582"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-50046"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-50243"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-50248"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-50251"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-55708"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-55717"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-55990"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-56416"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-56444"
    }
  ],
  "schema_version": "1.7.2",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
      "type": "CVSS_V3"
    }
  ],
  "summary": "unbound security update",
  "upstream": [
    "CVE-2026-40691",
    "CVE-2026-42955",
    "CVE-2026-44621",
    "CVE-2026-44687",
    "CVE-2026-44690",
    "CVE-2026-46582",
    "CVE-2026-50046",
    "CVE-2026-50243",
    "CVE-2026-50248",
    "CVE-2026-50251",
    "CVE-2026-55708",
    "CVE-2026-55717",
    "CVE-2026-55990",
    "CVE-2026-56416",
    "CVE-2026-56444"
  ]
}