ubuntu-cve-2026-5947
Vulnerability from osv_ubuntu
Published
2026-05-20 00:00
Modified
2026-06-30 16:18
Summary
Details

Undefined behavior may result due to a race condition leading to a use-after-free violation. If BIND receives an incoming DNS message signed with SIG(0), it begins work to validate that signature. If, during that validation, the "recursive-clients" limit is reached (as would occur during a query flood), and that same DNS message is discarded per the limit, there is a brief window of time while the SIG(0) validation may attempt to read the now-discarded DNS message. This issue affects BIND 9 versions 9.20.0 through 9.20.22, 9.21.0 through 9.21.21, and 9.20.9-S1 through 9.20.22-S1. BIND 9 versions 9.18.28 through 9.18.49 and 9.18.28-S1 through 9.18.49-S1 are NOT affected.

Severity
7.5 (High)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
7.5 (High)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
5.9 (Medium)
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
N/A (UNKNOWN)
medium
References
To clipboard 

{
  "affected": [
    {
      "ecosystem_specific": {
        "availability": "No subscription required",
        "binaries": [
          {
            "binary_name": "bind9",
            "binary_version": "1:9.20.11-1ubuntu2.4"
          },
          {
            "binary_name": "bind9-dnsutils",
            "binary_version": "1:9.20.11-1ubuntu2.4"
          },
          {
            "binary_name": "bind9-host",
            "binary_version": "1:9.20.11-1ubuntu2.4"
          },
          {
            "binary_name": "bind9-libs",
            "binary_version": "1:9.20.11-1ubuntu2.4"
          },
          {
            "binary_name": "bind9-utils",
            "binary_version": "1:9.20.11-1ubuntu2.4"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:25.10",
        "name": "bind9",
        "purl": "pkg:deb/ubuntu/bind9@1:9.20.11-1ubuntu2.4?arch=source\u0026distro=questing"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "1:9.20.11-1ubuntu2.4"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "1:9.20.4-3ubuntu1",
        "1:9.20.4-3ubuntu2",
        "1:9.20.4-3ubuntu3",
        "1:9.20.9-2ubuntu1",
        "1:9.20.10-1ubuntu1",
        "1:9.20.11-1ubuntu1",
        "1:9.20.11-1ubuntu2",
        "1:9.20.11-1ubuntu2.1",
        "1:9.20.11-1ubuntu2.2"
      ]
    },
    {
      "ecosystem_specific": {
        "availability": "No subscription required",
        "binaries": [
          {
            "binary_name": "bind9",
            "binary_version": "1:9.20.18-1ubuntu2.1"
          },
          {
            "binary_name": "bind9-dnsutils",
            "binary_version": "1:9.20.18-1ubuntu2.1"
          },
          {
            "binary_name": "bind9-host",
            "binary_version": "1:9.20.18-1ubuntu2.1"
          },
          {
            "binary_name": "bind9-libs",
            "binary_version": "1:9.20.18-1ubuntu2.1"
          },
          {
            "binary_name": "bind9-utils",
            "binary_version": "1:9.20.18-1ubuntu2.1"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:26.04:LTS",
        "name": "bind9",
        "purl": "pkg:deb/ubuntu/bind9@1:9.20.18-1ubuntu2.1?arch=source\u0026distro=resolute"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "1:9.20.18-1ubuntu2.1"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "1:9.20.11-1ubuntu2",
        "1:9.20.11-1ubuntu3",
        "1:9.20.18-1ubuntu1",
        "1:9.20.18-1ubuntu2"
      ]
    }
  ],
  "aliases": [],
  "details": "Undefined behavior may result due to a race condition leading to a use-after-free violation.  If BIND receives an incoming DNS message signed with SIG(0), it begins work to validate that signature.  If, during that validation, the \"recursive-clients\" limit is reached (as would occur during a query flood), and that same DNS message is discarded per the limit, there is a brief window of time while the SIG(0) validation may attempt to read the now-discarded DNS message. This issue affects BIND 9 versions 9.20.0 through 9.20.22, 9.21.0 through 9.21.21, and 9.20.9-S1 through 9.20.22-S1. BIND 9 versions 9.18.28 through 9.18.49 and 9.18.28-S1 through 9.18.49-S1 are NOT affected.",
  "id": "UBUNTU-CVE-2026-5947",
  "modified": "2026-06-30T16:18:37Z",
  "published": "2026-05-20T00:00:00Z",
  "references": [
    {
      "type": "REPORT",
      "url": "https://ubuntu.com/security/CVE-2026-5947"
    },
    {
      "type": "REPORT",
      "url": "https://www.cve.org/CVERecord?id=CVE-2026-5947"
    },
    {
      "type": "REPORT",
      "url": "https://kb.isc.org/docs/cve-2026-5947"
    },
    {
      "type": "ADVISORY",
      "url": "https://ubuntu.com/security/notices/USN-8293-1"
    }
  ],
  "related": [
    "USN-8293-1"
  ],
  "schema_version": "1.7.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
      "type": "CVSS_V3"
    },
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
      "type": "CVSS_V3"
    },
    {
      "score": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H",
      "type": "CVSS_V3"
    },
    {
      "score": "medium",
      "type": "Ubuntu"
    }
  ],
  "upstream": [
    "CVE-2026-5947"
  ]
}



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