CVE-2026-11721

publishedCWE-1284

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.

Technical severity7.5 highCVSS 3.1 · NVD: [email protected]

Published2026-07-22Source updated 2026-11-02

Collected2026-11-021 attributed source

Fixes and workarounds

No remediation reported in collected sources.

Missing remediation information is not evidence that no patch exists.

Affected products and versions

Affected products, source version ranges and reporting authorities
Product	Versions	Authority
bind isc	≥ 9.11.0; ≤ 9.18.50 (affected, custom)	NVD
bind isc	≥ 9.11.3; ≤ 9.18.50 (affected, custom)	NVD
bind isc	≥ 9.20.0; ≤ 9.20.24 (affected, custom)	NVD
bind isc	≥ 9.20.9; ≤ 9.20.24 (affected, custom)	NVD
bind isc	≥ 9.21.0; ≤ 9.21.23 (affected, custom)	NVD

Version ranges are source assertions. Check the vendor advisory and your installed configuration before determining exposure.

NVD applicability configurations (1)

These expressions retain AND/OR operators, negation, and required environmental products. A listed product is not sufficient to establish exposure when additional conditions apply.

[
  {
    "negate": false,
    "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:*:*:*:*:supported_preview:*:*:*",
            "versionEndIncluding": "9.18.50",
            "versionStartIncluding": "9.11.3",
            "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:*:*:*:*:supported_preview:*:*:*",
            "versionEndIncluding": "9.20.24",
            "versionStartIncluding": "9.20.9",
            "vulnerable": true
          },
          {
            "criteria": "cpe:2.3:a:isc:bind:*:*:*:*:-:*:*:*",
            "versionEndIncluding": "9.21.23",
            "versionStartIncluding": "9.21.0",
            "vulnerable": true
          }
        ],
        "negate": false,
        "operator": "OR"
      }
    ],
    "operator": "OR"
  }
]

CVSS assessments

CVSS scores, vectors and reporting authorities
Version / score	Vector	Authority
3.1 / 7.5 high	`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N`	NVD: [email protected]

Exploit evidence

No exploit evidence in collected sources. This is not proof of no exploitation.

References

https://downloads.isc.org/isc/bind9/9.20.26[email protected] · Product
https://downloads.isc.org/isc/bind9/9.21.24[email protected] · Product
https://kb.isc.org/docs/cve-2026-11721[email protected] · Vendor Advisory

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