Vulnerability-Lookup

GHSA-CQ66-H8MJ-77HH

Vulnerability from github – Published: 2026-07-22 15:31 – Updated: 2026-07-22 15:31

Details

It is possible for an attacker's zone to respond to a query with an RRSIG that has a smaller number of labels than the zone in which the RRSIG is contained. This causes named to produce a wildcard name for a zone that is shorter than the attacker's zone, which can result in cache poisoning. For this attack to have any effect, the resolver under attack must have set synth-from-dnssec yes; (which is the default). This issue affects BIND 9 versions 9.11.0 through 9.18.50, 9.20.0 through 9.20.24, 9.21.0 through 9.21.23, 9.11.3-S1 through 9.18.50-S1, and 9.20.9-S1 through 9.20.24-S1.

Severity

7.5 (High)


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

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{
  "affected": [],
  "aliases": [
    "CVE-2026-11721"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-1284"
    ],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-07-22T15:16:51Z",
    "severity": "HIGH"
  },
  "details": "It is possible for an attacker\u0027s zone to respond to a query with an RRSIG that has a smaller number of labels than the zone in which the RRSIG is contained. This causes `named` to produce a wildcard name for a zone that is shorter than the attacker\u0027s zone, which can result in cache poisoning. For this attack to have any effect, the resolver under attack must have set `synth-from-dnssec yes;` (which is the default).\nThis issue affects BIND 9 versions 9.11.0 through 9.18.50, 9.20.0 through 9.20.24, 9.21.0 through 9.21.23, 9.11.3-S1 through 9.18.50-S1, and 9.20.9-S1 through 9.20.24-S1.",
  "id": "GHSA-cq66-h8mj-77hh",
  "modified": "2026-07-22T15:31:26Z",
  "published": "2026-07-22T15:31:26Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-11721"
    },
    {
      "type": "WEB",
      "url": "https://downloads.isc.org/isc/bind9/9.20.26"
    },
    {
      "type": "WEB",
      "url": "https://downloads.isc.org/isc/bind9/9.21.24"
    },
    {
      "type": "WEB",
      "url": "https://kb.isc.org/docs/cve-2026-11721"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N",
      "type": "CVSS_V3"
    }
  ]
}

CVE-2026-11721 (GCVE-0-2026-11721)

Vulnerability from cvelistv5 – Published: 2026-07-22 14:13 – Updated: 2026-07-22 18:52

Title

Cache poisoning possible with label count discrepancy, RRSIG, and wildcards

Summary

It is possible for an attacker's zone to respond to a query with an RRSIG that has a smaller number of labels than the zone in which the RRSIG is contained. This causes `named` to produce a wildcard name for a zone that is shorter than the attacker's zone, which can result in cache poisoning. For this attack to have any effect, the resolver under attack must have set `synth-from-dnssec yes;` (which is the default). This issue affects BIND 9 versions 9.11.0 through 9.18.50, 9.20.0 through 9.20.24, 9.21.0 through 9.21.23, 9.11.3-S1 through 9.18.50-S1, and 9.20.9-S1 through 9.20.24-S1.

Severity

7.5 (High)


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

SSVC

Exploitation: none Automatable: yes Technical Impact: partial

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2026-07-22 18:52 UTC

CWE

CWE-1284 - Improper Validation of Specified Quantity in Input

Assigner

isc CNA under the mitre root

CNA scorecard A 95/100 over 33 records in the last 180 days details

References

3 references

URL	Tags
https://kb.isc.org/docs/cve-2026-11721	vendor-advisory
https://downloads.isc.org/isc/bind9/9.20.26	patch
https://downloads.isc.org/isc/bind9/9.21.24	patch

Impacted products

1 product

Vendor	Product	Version
ISC	BIND 9	Affected: 9.11.0 , ≤ 9.18.50 (custom) Affected: 9.20.0 , ≤ 9.20.24 (custom) Affected: 9.21.0 , ≤ 9.21.23 (custom) Affected: 9.11.3-S1 , ≤ 9.18.50-S1 (custom) Affected: 9.20.9-S1 , ≤ 9.20.24-S1 (custom) cpe:2.3:a:isc:bind:::::::: cpe:2.3:a:isc:bind:::::::: cpe:2.3:a:isc:bind:::::::: cpe:2.3:a:isc:bind:::::::: cpe:2.3:a:isc:bind::::::::

Date Public

2026-07-22 00:00

Credits

ISC would like to thank Qifan Zhang of Palo Alto Networks for bringing this vulnerability to our attention.

Show details on NVD website

JSON

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{
  "containers": {
    "adp": [
      {
        "metrics": [
          {
            "other": {
              "content": {
                "id": "CVE-2026-11721",
                "options": [
                  {
                    "Exploitation": "none"
                  },
                  {
                    "Automatable": "yes"
                  },
                  {
                    "Technical Impact": "partial"
                  }
                ],
                "role": "CISA Coordinator",
                "timestamp": "2026-07-22T18:52:35.390125Z",
                "version": "2.0.3"
              },
              "type": "ssvc"
            }
          }
        ],
        "providerMetadata": {
          "dateUpdated": "2026-07-22T18:52:46.888Z",
          "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
          "shortName": "CISA-ADP"
        },
        "title": "CISA ADP Vulnrichment"
      }
    ],
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "BIND 9",
          "vendor": "ISC",
          "versions": [
            {
              "lessThanOrEqual": "9.18.50",
              "status": "affected",
              "version": "9.11.0",
              "versionType": "custom"
            },
            {
              "lessThanOrEqual": "9.20.24",
              "status": "affected",
              "version": "9.20.0",
              "versionType": "custom"
            },
            {
              "lessThanOrEqual": "9.21.23",
              "status": "affected",
              "version": "9.21.0",
              "versionType": "custom"
            },
            {
              "lessThanOrEqual": "9.18.50-S1",
              "status": "affected",
              "version": "9.11.3-S1",
              "versionType": "custom"
            },
            {
              "lessThanOrEqual": "9.20.24-S1",
              "status": "affected",
              "version": "9.20.9-S1",
              "versionType": "custom"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
                {
                  "criteria": "cpe:2.3:a:isc:bind:*:*:*:*:*:*:*:*",
                  "versionEndIncluding": "9.18.50",
                  "versionStartIncluding": "9.11.0",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:a:isc:bind:*:*:*:*:*:*:*:*",
                  "versionEndIncluding": "9.20.24",
                  "versionStartIncluding": "9.20.0",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:a:isc:bind:*:*:*:*:*:*:*:*",
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                  "versionStartIncluding": "9.21.0",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:a:isc:bind:*:*:*:*:*:*:*:*",
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                  "versionStartIncluding": "9.11.3-S1",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:a:isc:bind:*:*:*:*:*:*:*:*",
                  "versionEndIncluding": "9.20.24-S1",
                  "versionStartIncluding": "9.20.9-S1",
                  "vulnerable": true
                }
              ],
              "operator": "OR"
            }
          ]
        }
      ],
      "credits": [
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          "lang": "en",
          "value": "ISC would like to thank Qifan Zhang of Palo Alto Networks for bringing this vulnerability to our attention."
        }
      ],
      "datePublic": "2026-07-22T00:00:00.000Z",
      "descriptions": [
        {
          "lang": "en",
          "value": "It is possible for an attacker\u0027s zone to respond to a query with an RRSIG that has a smaller number of labels than the zone in which the RRSIG is contained. This causes `named` to produce a wildcard name for a zone that is shorter than the attacker\u0027s zone, which can result in cache poisoning. For this attack to have any effect, the resolver under attack must have set `synth-from-dnssec yes;` (which is the default).\nThis issue affects BIND 9 versions 9.11.0 through 9.18.50, 9.20.0 through 9.20.24, 9.21.0 through 9.21.23, 9.11.3-S1 through 9.18.50-S1, and 9.20.9-S1 through 9.20.24-S1."
        }
      ],
      "exploits": [
        {
          "lang": "en",
          "value": "We are not aware of any active exploits."
        }
      ],
      "impacts": [
        {
          "descriptions": [
            {
              "lang": "en",
              "value": "Potential cache poisoning."
            }
          ]
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "attackComplexity": "LOW",
            "attackVector": "NETWORK",
            "availabilityImpact": "NONE",
            "baseScore": 7.5,
            "baseSeverity": "HIGH",
            "confidentialityImpact": "NONE",
            "integrityImpact": "HIGH",
            "privilegesRequired": "NONE",
            "scope": "UNCHANGED",
            "userInteraction": "NONE",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N",
            "version": "3.1"
          }
        }
      ],
      "problemTypes": [
        {
          "descriptions": [
            {
              "cweId": "CWE-1284",
              "description": "CWE-1284 Improper Validation of Specified Quantity in Input",
              "lang": "en",
              "type": "CWE"
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-07-22T14:13:08.748Z",
        "orgId": "404fd4d2-a609-4245-b543-2c944a302a22",
        "shortName": "isc"
      },
      "references": [
        {
          "name": "CVE-2026-11721",
          "tags": [
            "vendor-advisory"
          ],
          "url": "https://kb.isc.org/docs/cve-2026-11721"
        },
        {
          "tags": [
            "patch"
          ],
          "url": "https://downloads.isc.org/isc/bind9/9.20.26"
        },
        {
          "tags": [
            "patch"
          ],
          "url": "https://downloads.isc.org/isc/bind9/9.21.24"
        }
      ],
      "solutions": [
        {
          "lang": "en",
          "value": "Upgrade to the patched release most closely related to your current version of BIND 9: 9.20.26, 9.21.24, or 9.20.26-S1."
        }
      ],
      "source": {
        "discovery": "EXTERNAL"
      },
      "title": "Cache poisoning possible with label count discrepancy, RRSIG, and wildcards",
      "workarounds": [
        {
          "lang": "en",
          "value": "No workarounds known."
        }
      ],
      "x_generator": {
        "engine": "cvelib 1.8.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "404fd4d2-a609-4245-b543-2c944a302a22",
    "assignerShortName": "isc",
    "cveId": "CVE-2026-11721",
    "datePublished": "2026-07-22T14:13:08.748Z",
    "dateReserved": "2026-06-09T01:19:47.697Z",
    "dateUpdated": "2026-07-22T18:52:46.888Z",
    "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.

Vulnerability timeline

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The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base model, served locally by ML-Gateway. They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
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