Vulnerability-Lookup

CVE-2026-42923 (GCVE-0-2026-42923)

Vulnerability from cvelistv5 – Published: 2026-05-20 09:20 – Updated: 2026-05-20 12:10

Title

Degradation of service with unbounded NSEC3 hash calculations

Summary

NLnet Labs Unbound up to and including version 1.25.0 has a vulnerability in the DNSSEC validator where the code path to consult the negative cache for DS records does not take into account the limit on NSEC3 hash calculations introduced in 1.19.1. This leads to degradation of service during the attack. An adversary that controls a DNSSEC signed zone can exploit this by signing NSEC3 records with acceptably high iterations for child delegations and querying a vulnerable Unbound. Unbound will keep performing the allowed hash calculations on the NSEC3 records and will not limit the work by the mitigation introduced in 1.19.1. As a side effect, a global lock for the negative cache will be held for the duration of the hashing, blocking other threads that need to consult the negative cache. Coordinated attacks could raise the vulnerability to denial of service. Unbound 1.25.1 contains a patch with a fix to bound the vulnerable code path with the existing limit for NSEC3 hash calculations.

Severity ?

6.9 (Medium)


                        
                          CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N/U:Amber

CWE

CWE-407 - Inefficient Algorithmic Complexity

Assigner

NLnet Labs

References

1 reference

URL	Tags
https://www.nlnetlabs.nl/downloads/unbound/CVE-20…	vendor-advisory

Impacted products

1 product

Vendor	Product	Version
NLnet Labs	Unbound	Affected: 0 , < 1.25.1 (semver)

Date Public ?

2026-05-20 00:00

Credits

Qifan Zhang (Palo Alto Networks)

Show details on NVD website

JSON

To clipboard

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FKIE_CVE-2026-42923

Vulnerability from fkie_nvd - Published: 2026-05-20 10:16 - Updated: 2026-05-20 22:50

Severity ?

5.3 (Medium) - CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

Summary

References

	URL	Tags
	sep@nlnetlabs.nl	https://www.nlnetlabs.nl/downloads/unbound/CVE-2026-42923.txt	Mitigation, Vendor Advisory

Impacted products

	Vendor	Product	Version
	nlnetlabs	unbound	*

JSON

To clipboard

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          "cpeMatch": [
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GHSA-8F6W-8H24-FW66

Vulnerability from github – Published: 2026-05-20 12:30 – Updated: 2026-05-21 00:30

Details

Severity ?

5.3 (Medium)


                  
                    CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

6.9 (Medium)


                  
                    CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N/U:Amber

Show details on source website

JSON

To clipboard

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  "affected": [],
  "aliases": [
    "CVE-2026-42923"
  ],
  "database_specific": {
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    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-05-20T10:16:27Z",
    "severity": "MODERATE"
  },
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  "id": "GHSA-8f6w-8h24-fw66",
  "modified": "2026-05-21T00:30:27Z",
  "published": "2026-05-20T12:30:36Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-42923"
    },
    {
      "type": "WEB",
      "url": "https://www.nlnetlabs.nl/downloads/unbound/CVE-2026-42923.txt"
    }
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      "type": "CVSS_V3"
    },
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}

WID-SEC-W-2026-1599

Vulnerability from csaf_certbund - Published: 2026-05-19 22:00 - Updated: 2026-05-20 22:00

Summary

Unbound: Mehrere Schwachstellen ermöglichen nicht spezifizierten Angriff

Severity

Mittel

Notes

Das BSI ist als Anbieter für die eigenen, zur Nutzung bereitgestellten Inhalte nach den allgemeinen Gesetzen verantwortlich. Nutzerinnen und Nutzer sind jedoch dafür verantwortlich, die Verwendung und/oder die Umsetzung der mit den Inhalten bereitgestellten Informationen sorgfältig im Einzelfall zu prüfen.

Produktbeschreibung: Unbound ist ein validierender, rekursiver DNS-Resolver.

Angriff: Ein Angreifer kann mehrere Schwachstellen in Unbound ausnutzen, um einen nicht näher spezifizierten Angriff durchzuführen.

Betroffene Betriebssysteme: - Linux - UNIX

CVE-2026-32792

Affected products

Known affected 4 products

Product	Identifier	Version
Red Hat Enterprise Linux Red Hat	`cpe:/o:redhat:enterprise_linux:-`	—
Open Source Unbound <1.25.1 Open Source / Unbound		<1.25.1
Ubuntu Linux Ubuntu	`cpe:/o:canonical:ubuntu_linux:-`	—
Fedora Linux Fedora	`cpe:/o:fedoraproject:fedora:-`	—

CVE-2026-33278

Affected products

Known affected 4 products

Product	Identifier	Version
Red Hat Enterprise Linux Red Hat	`cpe:/o:redhat:enterprise_linux:-`	—
Open Source Unbound <1.25.1 Open Source / Unbound		<1.25.1
Ubuntu Linux Ubuntu	`cpe:/o:canonical:ubuntu_linux:-`	—
Fedora Linux Fedora	`cpe:/o:fedoraproject:fedora:-`	—

CVE-2026-40622

Affected products

Known affected 4 products

Product	Identifier	Version
Red Hat Enterprise Linux Red Hat	`cpe:/o:redhat:enterprise_linux:-`	—
Open Source Unbound <1.25.1 Open Source / Unbound		<1.25.1
Ubuntu Linux Ubuntu	`cpe:/o:canonical:ubuntu_linux:-`	—
Fedora Linux Fedora	`cpe:/o:fedoraproject:fedora:-`	—

CVE-2026-41292

Affected products

Known affected 4 products

Product	Identifier	Version
Red Hat Enterprise Linux Red Hat	`cpe:/o:redhat:enterprise_linux:-`	—
Open Source Unbound <1.25.1 Open Source / Unbound		<1.25.1
Ubuntu Linux Ubuntu	`cpe:/o:canonical:ubuntu_linux:-`	—
Fedora Linux Fedora	`cpe:/o:fedoraproject:fedora:-`	—

CVE-2026-42534

Affected products

Known affected 4 products

Product	Identifier	Version
Red Hat Enterprise Linux Red Hat	`cpe:/o:redhat:enterprise_linux:-`	—
Open Source Unbound <1.25.1 Open Source / Unbound		<1.25.1
Ubuntu Linux Ubuntu	`cpe:/o:canonical:ubuntu_linux:-`	—
Fedora Linux Fedora	`cpe:/o:fedoraproject:fedora:-`	—

CVE-2026-42923

Affected products

Known affected 4 products

Product	Identifier	Version
Red Hat Enterprise Linux Red Hat	`cpe:/o:redhat:enterprise_linux:-`	—
Open Source Unbound <1.25.1 Open Source / Unbound		<1.25.1
Ubuntu Linux Ubuntu	`cpe:/o:canonical:ubuntu_linux:-`	—
Fedora Linux Fedora	`cpe:/o:fedoraproject:fedora:-`	—

CVE-2026-42944

Affected products

Known affected 4 products

Product	Identifier	Version
Red Hat Enterprise Linux Red Hat	`cpe:/o:redhat:enterprise_linux:-`	—
Open Source Unbound <1.25.1 Open Source / Unbound		<1.25.1
Ubuntu Linux Ubuntu	`cpe:/o:canonical:ubuntu_linux:-`	—
Fedora Linux Fedora	`cpe:/o:fedoraproject:fedora:-`	—

CVE-2026-42959

Affected products

Known affected 4 products

Product	Identifier	Version
Red Hat Enterprise Linux Red Hat	`cpe:/o:redhat:enterprise_linux:-`	—
Open Source Unbound <1.25.1 Open Source / Unbound		<1.25.1
Ubuntu Linux Ubuntu	`cpe:/o:canonical:ubuntu_linux:-`	—
Fedora Linux Fedora	`cpe:/o:fedoraproject:fedora:-`	—

CVE-2026-42960

Affected products

Known affected 4 products

Product	Identifier	Version
Red Hat Enterprise Linux Red Hat	`cpe:/o:redhat:enterprise_linux:-`	—
Open Source Unbound <1.25.1 Open Source / Unbound		<1.25.1
Ubuntu Linux Ubuntu	`cpe:/o:canonical:ubuntu_linux:-`	—
Fedora Linux Fedora	`cpe:/o:fedoraproject:fedora:-`	—

CVE-2026-44390

Affected products

Known affected 4 products

Product	Identifier	Version
Red Hat Enterprise Linux Red Hat	`cpe:/o:redhat:enterprise_linux:-`	—
Open Source Unbound <1.25.1 Open Source / Unbound		<1.25.1
Ubuntu Linux Ubuntu	`cpe:/o:canonical:ubuntu_linux:-`	—
Fedora Linux Fedora	`cpe:/o:fedoraproject:fedora:-`	—

CVE-2026-44608

Affected products

Known affected 4 products

Product	Identifier	Version
Red Hat Enterprise Linux Red Hat	`cpe:/o:redhat:enterprise_linux:-`	—
Open Source Unbound <1.25.1 Open Source / Unbound		<1.25.1
Ubuntu Linux Ubuntu	`cpe:/o:canonical:ubuntu_linux:-`	—
Fedora Linux Fedora	`cpe:/o:fedoraproject:fedora:-`	—

References

7 references

URL	Category
https://wid.cert-bund.de/.well-known/csaf/white/2…	self
https://wid.cert-bund.de/portal/wid/securityadvis…	self
https://nlnetlabs.nl/news/2026/May/20/unbound-1.2…	external
https://ubuntu.com/security/notices/USN-8282-1	external
https://bodhi.fedoraproject.org/updates/FEDORA-20…	external
https://access.redhat.com/errata/RHSA-2026:19752	external
https://bodhi.fedoraproject.org/updates/FEDORA-20…	external

JSON

To clipboard

{
  "document": {
    "aggregate_severity": {
      "text": "mittel"
    },
    "category": "csaf_base",
    "csaf_version": "2.0",
    "distribution": {
      "tlp": {
        "label": "WHITE",
        "url": "https://www.first.org/tlp/"
      }
    },
    "lang": "de-DE",
    "notes": [
      {
        "category": "legal_disclaimer",
        "text": "Das BSI ist als Anbieter f\u00fcr die eigenen, zur Nutzung bereitgestellten Inhalte nach den allgemeinen Gesetzen verantwortlich. Nutzerinnen und Nutzer sind jedoch daf\u00fcr verantwortlich, die Verwendung und/oder die Umsetzung der mit den Inhalten bereitgestellten Informationen sorgf\u00e4ltig im Einzelfall zu pr\u00fcfen."
      },
      {
        "category": "description",
        "text": "Unbound ist ein validierender, rekursiver DNS-Resolver.",
        "title": "Produktbeschreibung"
      },
      {
        "category": "summary",
        "text": "Ein Angreifer kann mehrere Schwachstellen in Unbound ausnutzen, um einen nicht n\u00e4her spezifizierten Angriff durchzuf\u00fchren.",
        "title": "Angriff"
      },
      {
        "category": "general",
        "text": "- Linux\n- UNIX",
        "title": "Betroffene Betriebssysteme"
      }
    ],
    "publisher": {
      "category": "other",
      "contact_details": "csaf-provider@cert-bund.de",
      "name": "Bundesamt f\u00fcr Sicherheit in der Informationstechnik",
      "namespace": "https://www.bsi.bund.de"
    },
    "references": [
      {
        "category": "self",
        "summary": "WID-SEC-W-2026-1599 - CSAF Version",
        "url": "https://wid.cert-bund.de/.well-known/csaf/white/2026/wid-sec-w-2026-1599.json"
      },
      {
        "category": "self",
        "summary": "WID-SEC-2026-1599 - Portal Version",
        "url": "https://wid.cert-bund.de/portal/wid/securityadvisory?name=WID-SEC-2026-1599"
      },
      {
        "category": "external",
        "summary": "Unbound 1.25.1 release vom 2026-05-19",
        "url": "https://nlnetlabs.nl/news/2026/May/20/unbound-1.25.1-released/"
      },
      {
        "category": "external",
        "summary": "Ubuntu Security Notice USN-8282-1 vom 2026-05-20",
        "url": "https://ubuntu.com/security/notices/USN-8282-1"
      },
      {
        "category": "external",
        "summary": "Fedora Security Advisory FEDORA-2026-3223DED15E vom 2026-05-20",
        "url": "https://bodhi.fedoraproject.org/updates/FEDORA-2026-3223ded15e"
      },
      {
        "category": "external",
        "summary": "Red Hat Security Advisory RHSA-2026:19752 vom 2026-05-20",
        "url": "https://access.redhat.com/errata/RHSA-2026:19752"
      },
      {
        "category": "external",
        "summary": "Fedora Security Advisory FEDORA-2026-49F37E16AA vom 2026-05-20",
        "url": "https://bodhi.fedoraproject.org/updates/FEDORA-2026-49f37e16aa"
      }
    ],
    "source_lang": "en-US",
    "title": "Unbound: Mehrere Schwachstellen erm\u00f6glichen nicht spezifizierten Angriff",
    "tracking": {
      "current_release_date": "2026-05-20T22:00:00.000+00:00",
      "generator": {
        "date": "2026-05-21T07:35:44.356+00:00",
        "engine": {
          "name": "BSI-WID",
          "version": "1.6.0"
        }
      },
      "id": "WID-SEC-W-2026-1599",
      "initial_release_date": "2026-05-19T22:00:00.000+00:00",
      "revision_history": [
        {
          "date": "2026-05-19T22:00:00.000+00:00",
          "number": "1",
          "summary": "Initiale Fassung"
        },
        {
          "date": "2026-05-20T22:00:00.000+00:00",
          "number": "2",
          "summary": "Neue Updates von Open Source, Ubuntu, European Union Vulnerability Database, Fedora und Red Hat aufgenommen"
        }
      ],
      "status": "final",
      "version": "2"
    }
  },
  "product_tree": {
    "branches": [
      {
        "branches": [
          {
            "category": "product_name",
            "name": "Fedora Linux",
            "product": {
              "name": "Fedora Linux",
              "product_id": "74185",
              "product_identification_helper": {
                "cpe": "cpe:/o:fedoraproject:fedora:-"
              }
            }
          }
        ],
        "category": "vendor",
        "name": "Fedora"
      },
      {
        "branches": [
          {
            "branches": [
              {
                "category": "product_version_range",
                "name": "\u003c1.25.1",
                "product": {
                  "name": "Open Source Unbound \u003c1.25.1",
                  "product_id": "T054382"
                }
              },
              {
                "category": "product_version",
                "name": "1.25.1",
                "product": {
                  "name": "Open Source Unbound 1.25.1",
                  "product_id": "T054382-fixed",
                  "product_identification_helper": {
                    "cpe": "cpe:/a:nlnetlabs:unbound:1.25.1"
                  }
                }
              }
            ],
            "category": "product_name",
            "name": "Unbound"
          }
        ],
        "category": "vendor",
        "name": "Open Source"
      },
      {
        "branches": [
          {
            "category": "product_name",
            "name": "Red Hat Enterprise Linux",
            "product": {
              "name": "Red Hat Enterprise Linux",
              "product_id": "67646",
              "product_identification_helper": {
                "cpe": "cpe:/o:redhat:enterprise_linux:-"
              }
            }
          }
        ],
        "category": "vendor",
        "name": "Red Hat"
      },
      {
        "branches": [
          {
            "category": "product_name",
            "name": "Ubuntu Linux",
            "product": {
              "name": "Ubuntu Linux",
              "product_id": "T000126",
              "product_identification_helper": {
                "cpe": "cpe:/o:canonical:ubuntu_linux:-"
              }
            }
          }
        ],
        "category": "vendor",
        "name": "Ubuntu"
      }
    ]
  },
  "vulnerabilities": [
    {
      "cve": "CVE-2026-32792",
      "product_status": {
        "known_affected": [
          "67646",
          "T054382",
          "T000126",
          "74185"
        ]
      },
      "release_date": "2026-05-19T22:00:00.000+00:00",
      "title": "CVE-2026-32792"
    },
    {
      "cve": "CVE-2026-33278",
      "product_status": {
        "known_affected": [
          "67646",
          "T054382",
          "T000126",
          "74185"
        ]
      },
      "release_date": "2026-05-19T22:00:00.000+00:00",
      "title": "CVE-2026-33278"
    },
    {
      "cve": "CVE-2026-40622",
      "product_status": {
        "known_affected": [
          "67646",
          "T054382",
          "T000126",
          "74185"
        ]
      },
      "release_date": "2026-05-19T22:00:00.000+00:00",
      "title": "CVE-2026-40622"
    },
    {
      "cve": "CVE-2026-41292",
      "product_status": {
        "known_affected": [
          "67646",
          "T054382",
          "T000126",
          "74185"
        ]
      },
      "release_date": "2026-05-19T22:00:00.000+00:00",
      "title": "CVE-2026-41292"
    },
    {
      "cve": "CVE-2026-42534",
      "product_status": {
        "known_affected": [
          "67646",
          "T054382",
          "T000126",
          "74185"
        ]
      },
      "release_date": "2026-05-19T22:00:00.000+00:00",
      "title": "CVE-2026-42534"
    },
    {
      "cve": "CVE-2026-42923",
      "product_status": {
        "known_affected": [
          "67646",
          "T054382",
          "T000126",
          "74185"
        ]
      },
      "release_date": "2026-05-19T22:00:00.000+00:00",
      "title": "CVE-2026-42923"
    },
    {
      "cve": "CVE-2026-42944",
      "product_status": {
        "known_affected": [
          "67646",
          "T054382",
          "T000126",
          "74185"
        ]
      },
      "release_date": "2026-05-19T22:00:00.000+00:00",
      "title": "CVE-2026-42944"
    },
    {
      "cve": "CVE-2026-42959",
      "product_status": {
        "known_affected": [
          "67646",
          "T054382",
          "T000126",
          "74185"
        ]
      },
      "release_date": "2026-05-19T22:00:00.000+00:00",
      "title": "CVE-2026-42959"
    },
    {
      "cve": "CVE-2026-42960",
      "product_status": {
        "known_affected": [
          "67646",
          "T054382",
          "T000126",
          "74185"
        ]
      },
      "release_date": "2026-05-19T22:00:00.000+00:00",
      "title": "CVE-2026-42960"
    },
    {
      "cve": "CVE-2026-44390",
      "product_status": {
        "known_affected": [
          "67646",
          "T054382",
          "T000126",
          "74185"
        ]
      },
      "release_date": "2026-05-19T22:00:00.000+00:00",
      "title": "CVE-2026-44390"
    },
    {
      "cve": "CVE-2026-44608",
      "product_status": {
        "known_affected": [
          "67646",
          "T054382",
          "T000126",
          "74185"
        ]
      },
      "release_date": "2026-05-19T22:00:00.000+00:00",
      "title": "CVE-2026-44608"
    }
  ]
}

Sightings

Author	Source	Type	Date	Other

Nomenclature

Seen: The vulnerability was mentioned, discussed, or observed by the user.
Confirmed: The vulnerability has been validated from an analyst's perspective.
Published Proof of Concept: A public proof of concept is available for this vulnerability.
Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
Not confirmed: The user expressed doubt about the validity of the vulnerability.
Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

Detection rules are retrieved from Rulezet.

Action not permitted

CVE-2026-42923 (GCVE-0-2026-42923)

FKIE_CVE-2026-42923

GHSA-8F6W-8H24-FW66

WID-SEC-W-2026-1599

Tags

Sightings

Nomenclature