CVE-2026-11721

Status: Undergoing AnalysisHigh (7.5)—

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.

CVSS

Version: 3.1
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
Base score: 7.5

Exploitation probability (EPSS)

Probability of exploitation in the next 30 days: 0.40%
Percentile among all scored CVEs: 32
Score date: 10/6/2026

EPSS (Exploit Prediction Scoring System, FIRST) estimates how likely a vulnerability is to be exploited in the wild within 30 days. It complements CVSS (impact) and CISA KEV (confirmed exploitation).

🎯 ATT&CK techniques

How this vulnerability is exploited and what the attacker gains, in MITRE ATT&CK terms.

ExploitationT1190 Exploit Public-Facing Applicationinitial access60 %

Inferred by deterministic rules from the CVSS vector and CWE. Indicative only.

🛡️ ATT&CK mitigations that cover these techniques

Vulnerability Scanning Privileged Account Management Network Segmentation Limit Access to Resource Over Network Filter Network Traffic Application Isolation and Sandboxing

Affected technologies (1)

⚠ AI-inferred from the description — NVD hasn't analyzed this CVE yet, these aren't verified CPEs.

ISC — Bind^AI

CWEs

CWE-1284

References

Raw JSON (NVD)

Show

{
  "id": "CVE-2026-11721",
  "cveTags": [],
  "metrics": {
    "ssvcV203": [
      {
        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "ssvcData": {
          "id": "CVE-2026-11721",
          "role": "CISA Coordinator",
          "options": [
            {
              "exploitation": "none"
            },
            {
              "automatable": "yes"
            },
            {
              "technicalImpact": "partial"
            }
          ],
          "version": "2.0.3",
          "timestamp": "2026-07-22T18:52:35.390125Z"
        }
      }
    ],
    "cvssMetricV31": [
      {
        "type": "Secondary",
        "source": "security-officer@isc.org",
        "cvssData": {
          "scope": "UNCHANGED",
          "version": "3.1",
          "baseScore": 7.5,
          "attackVector": "NETWORK",
          "baseSeverity": "HIGH",
          "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N",
          "integrityImpact": "HIGH",
          "userInteraction": "NONE",
          "attackComplexity": "LOW",
          "availabilityImpact": "NONE",
          "privilegesRequired": "NONE",
          "confidentialityImpact": "NONE"
        },
        "impactScore": 3.6,
        "exploitabilityScore": 3.9
      }
    ]
  },
  "affected": [
    {
      "source": "security-officer@isc.org",
      "affectedData": [
        {
          "vendor": "ISC",
          "product": "BIND 9",
          "versions": [
            {
              "status": "affected",
              "version": "9.11.0",
              "versionType": "custom",
              "lessThanOrEqual": "9.18.50"
            },
            {
              "status": "affected",
              "version": "9.20.0",
              "versionType": "custom",
              "lessThanOrEqual": "9.20.24"
            },
            {
              "status": "affected",
              "version": "9.21.0",
              "versionType": "custom",
              "lessThanOrEqual": "9.21.23"
            },
            {
              "status": "affected",
              "version": "9.11.3-S1",
              "versionType": "custom",
              "lessThanOrEqual": "9.18.50-S1"
            },
            {
              "status": "affected",
              "version": "9.20.9-S1",
              "versionType": "custom",
              "lessThanOrEqual": "9.20.24-S1"
            }
          ],
          "defaultStatus": "unaffected"
        }
      ]
    }
  ],
  "published": "2026-07-22T15:16:51.837",
  "references": [
    {
      "url": "https://downloads.isc.org/isc/bind9/9.20.26",
      "source": "security-officer@isc.org"
    },
    {
      "url": "https://downloads.isc.org/isc/bind9/9.21.24",
      "source": "security-officer@isc.org"
    },
    {
      "url": "https://kb.isc.org/docs/cve-2026-11721",
      "source": "security-officer@isc.org"
    }
  ],
  "vulnStatus": "Undergoing Analysis",
  "weaknesses": [
    {
      "type": "Secondary",
      "source": "security-officer@isc.org",
      "description": [
        {
          "lang": "en",
          "value": "CWE-1284"
        }
      ]
    }
  ],
  "descriptions": [
    {
      "lang": "en",
      "value": "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).\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."
    }
  ],
  "lastModified": "2026-07-22T20:33:11.590",
  "sourceIdentifier": "security-officer@isc.org"
}