Vulnerability-Lookup

GHSA-H8MM-C463-WJQ3

Vulnerability from github – Published: 2026-04-28 22:44 – Updated: 2026-05-08 15:28

Summary

CoreDNS' transfer stanza selection uses lexicographic compare (subzone ACL bypass)

Details

Summary

CoreDNS' transfer plugin can select the wrong ACL stanza when both a parent zone and a more-specific subzone are configured. A permissive parent-zone transfer rule can override a restrictive subzone rule (name-dependent), allowing an unauthorized client to perform AXFR/IXFR for the subzone and retrieve its zone contents.

Details

In plugin/transfer/transfer.go, stanza selection is implemented by longestMatch(), which is documented as "longest zone match wins", but it actually chooses the winner via a lexicographic string comparison: - zone := "" // longest zone match wins (plugin/transfer/transfer.go) - if z > zone { zone = z; x = xfr } (plugin/transfer/transfer.go)

So, a parent zone like example.org. can beat a child zone like a.example.org. purely due to lexicographic ordering ("example.org." > "a.example.org."), even though the child zone is the longer/more specific suffix match. The bypass is data-dependent (some child labels will win, some will lose), making it operationally non-intuitive.

PoC

Adjust COREDNS_BIN in the PoC to point at right path (see the top-level const definitions for tunables as well)
Run python3 ./acl-repro.py
Expected output: *** Baseline (only subzone transfer rule) *** axfr a.example.org.: rcode=5 ancount=0 (expected REFUSED=5)

*** Candidate (add permissive parent transfer rule) *** axfr a.example.org.: rcode=0 ancount=5 (expected NOERROR=0 with ancount>0)

*** OK *** Subzone transfer ACL bypass reproduced: adding a permissive parent-zone stanza can override a stricter child-zone stanza due to lexicographic zone selection.

Impact

Unauthorized zone transfer can expose full zone contents to a remote network client that was intended to be denied by a subzone-specific transfer policy.

Severity ?

7.5 (High)


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

8.2 (High)


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

Show details on source website

JSON

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{
  "affected": [
    {
      "package": {
        "ecosystem": "Go",
        "name": "github.com/coredns/coredns"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "1.14.3"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-33489"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-862",
      "CWE-863"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-04-28T22:44:39Z",
    "nvd_published_at": "2026-05-05T20:16:36Z",
    "severity": "HIGH"
  },
  "details": "### Summary\nCoreDNS\u0027 transfer plugin can select the wrong ACL stanza when both a parent zone and a more-specific subzone are configured. A permissive parent-zone transfer rule can override a restrictive subzone rule (name-dependent), allowing an unauthorized client to perform AXFR/IXFR for the subzone and retrieve its zone contents.\n\n### Details\nIn plugin/transfer/transfer.go, stanza selection is implemented by longestMatch(), which is documented as \"longest zone match wins\", but it actually chooses the winner via a lexicographic string comparison:\n- zone := \"\" // longest zone match wins (plugin/transfer/transfer.go)\n- if z \u003e zone { zone = z; x = xfr } (plugin/transfer/transfer.go)\n\nSo, a parent zone like example.org. can beat a child zone like a.example.org. purely due to lexicographic ordering (\"example.org.\" \u003e \"a.example.org.\"), even though the child zone is the longer/more specific suffix match. The bypass is data-dependent (some child labels will win, some will lose), making it operationally non-intuitive.\n\n### PoC\n1. Adjust COREDNS_BIN in the PoC to point at right path (see the top-level const definitions for tunables as well)\n2. Run python3 ./acl-repro.py\n3. Expected output:\n*** Baseline (only subzone transfer rule) ***\naxfr a.example.org.: rcode=5 ancount=0 (expected REFUSED=5)\n\n*** Candidate (add permissive parent transfer rule) ***\naxfr a.example.org.: rcode=0 ancount=5 (expected NOERROR=0 with ancount\u003e0)\n\n*** OK ***\nSubzone transfer ACL bypass reproduced: adding a permissive parent-zone stanza can override a stricter child-zone stanza due to lexicographic zone selection.\n\n### Impact\nUnauthorized zone transfer can expose full zone contents to a remote network client that was intended to be denied by a subzone-specific transfer policy.",
  "id": "GHSA-h8mm-c463-wjq3",
  "modified": "2026-05-08T15:28:38Z",
  "published": "2026-04-28T22:44:39Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/coredns/coredns/security/advisories/GHSA-h8mm-c463-wjq3"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-33489"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/coredns/coredns"
    },
    {
      "type": "WEB",
      "url": "https://github.com/coredns/coredns/releases/tag/v1.14.3"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N",
      "type": "CVSS_V3"
    },
    {
      "score": "CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N",
      "type": "CVSS_V4"
    }
  ],
  "summary": "CoreDNS\u0027 transfer stanza selection uses lexicographic compare (subzone ACL bypass)"
}

CVE-2026-33489 (GCVE-0-2026-33489)

Vulnerability from cvelistv5 – Published: 2026-05-05 19:13 – Updated: 2026-05-05 19:43

Title

CoreDNS transfer plugin subzone ACL bypass via lexicographic zone comparison

Summary

CoreDNS is a DNS server that chains plugins. In versions prior to 1.14.3, the transfer plugin can select the wrong ACL stanza when both a parent zone and a more-specific subzone are configured. The longestMatch() function in plugin/transfer/transfer.go uses a lexicographic string comparison instead of an actual longest-suffix match to select the winning zone. As a result, a permissive parent-zone transfer rule can override a restrictive subzone rule depending on zone name ordering (e.g., "example.org." > "a.example.org." lexicographically). This allows an unauthorized remote client to perform AXFR/IXFR for the subzone and retrieve its full zone contents. This issue has been fixed in version 1.14.3.

Severity ?

8.2 (High)


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

CWE

CWE-863 - Incorrect Authorization

Assigner

GitHub_M

References

2 references

URL	Tags
https://github.com/coredns/coredns/security/advis…	x_refsource_CONFIRM
https://github.com/coredns/coredns/releases/tag/v1.14.3	x_refsource_MISC

Impacted products

1 product

Vendor	Product	Version
coredns	coredns	Affected: < 1.14.3

Show details on NVD website

JSON

To clipboard

{
  "containers": {
    "adp": [
      {
        "metrics": [
          {
            "other": {
              "content": {
                "id": "CVE-2026-33489",
                "options": [
                  {
                    "Exploitation": "poc"
                  },
                  {
                    "Automatable": "yes"
                  },
                  {
                    "Technical Impact": "partial"
                  }
                ],
                "role": "CISA Coordinator",
                "timestamp": "2026-05-05T19:43:02.806824Z",
                "version": "2.0.3"
              },
              "type": "ssvc"
            }
          }
        ],
        "providerMetadata": {
          "dateUpdated": "2026-05-05T19:43:06.361Z",
          "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
          "shortName": "CISA-ADP"
        },
        "references": [
          {
            "tags": [
              "exploit"
            ],
            "url": "https://github.com/coredns/coredns/security/advisories/GHSA-h8mm-c463-wjq3"
          }
        ],
        "title": "CISA ADP Vulnrichment"
      }
    ],
    "cna": {
      "affected": [
        {
          "product": "coredns",
          "vendor": "coredns",
          "versions": [
            {
              "status": "affected",
              "version": "\u003c 1.14.3"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "CoreDNS is a DNS server that chains plugins. In versions prior to 1.14.3, the transfer plugin can select the wrong ACL stanza when both a parent zone and a more-specific subzone are configured. The longestMatch() function in plugin/transfer/transfer.go uses a lexicographic string comparison instead of an actual longest-suffix match to select the winning zone. As a result, a permissive parent-zone transfer rule can override a restrictive subzone rule depending on zone name ordering (e.g., \"example.org.\" \u003e \"a.example.org.\" lexicographically). This allows an unauthorized remote client to perform AXFR/IXFR for the subzone and retrieve its full zone contents. This issue has been fixed in version 1.14.3."
        }
      ],
      "metrics": [
        {
          "cvssV4_0": {
            "attackComplexity": "LOW",
            "attackRequirements": "PRESENT",
            "attackVector": "NETWORK",
            "baseScore": 8.2,
            "baseSeverity": "HIGH",
            "privilegesRequired": "NONE",
            "subAvailabilityImpact": "NONE",
            "subConfidentialityImpact": "NONE",
            "subIntegrityImpact": "NONE",
            "userInteraction": "NONE",
            "vectorString": "CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N",
            "version": "4.0",
            "vulnAvailabilityImpact": "NONE",
            "vulnConfidentialityImpact": "HIGH",
            "vulnIntegrityImpact": "NONE"
          }
        }
      ],
      "problemTypes": [
        {
          "descriptions": [
            {
              "cweId": "CWE-863",
              "description": "CWE-863: Incorrect Authorization",
              "lang": "en",
              "type": "CWE"
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-05-05T19:13:48.461Z",
        "orgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
        "shortName": "GitHub_M"
      },
      "references": [
        {
          "name": "https://github.com/coredns/coredns/security/advisories/GHSA-h8mm-c463-wjq3",
          "tags": [
            "x_refsource_CONFIRM"
          ],
          "url": "https://github.com/coredns/coredns/security/advisories/GHSA-h8mm-c463-wjq3"
        },
        {
          "name": "https://github.com/coredns/coredns/releases/tag/v1.14.3",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/coredns/coredns/releases/tag/v1.14.3"
        }
      ],
      "source": {
        "advisory": "GHSA-h8mm-c463-wjq3",
        "discovery": "UNKNOWN"
      },
      "title": "CoreDNS transfer plugin subzone ACL bypass via lexicographic zone comparison"
    }
  },
  "cveMetadata": {
    "assignerOrgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
    "assignerShortName": "GitHub_M",
    "cveId": "CVE-2026-33489",
    "datePublished": "2026-05-05T19:13:48.461Z",
    "dateReserved": "2026-03-20T16:16:48.971Z",
    "dateUpdated": "2026-05-05T19:43:06.361Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}

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

GHSA-H8MM-C463-WJQ3

Summary

Details

PoC

Impact

CVE-2026-33489 (GCVE-0-2026-33489)

Tags

Sightings

Nomenclature