{
  "cveId": "CVE-2026-40691",
  "url": "https://patchblox.com/security/cve/CVE-2026-40691",
  "summary": "CVE-2026-40691 is fixed in 7 products on 1 platform, first by DEBIAN-CVE-2026-40691, released July 28, 2026. It is not reported as exploited. Patch Radar priority: High.",
  "title": "Packet of death for DNSCrypt over TCP",
  "description": "In Unbound 1.9.0 up to and including 1.25.1, when a DNSCrypt query is received over TCP, the routine that encrypts the reply in place fails to bound the reply length against the destination buffer size. The size clamp that protects the UDP path is not applied on the TCP path, so a reply larger than 65504 bytes is shifted forward by 48 bytes inside a buffer of capacity equal to \u0027msg-buffer-size\u0027, writing past the end of the heap allocation. A single malicious encrypted query crashes the resolver and lead to denial of service. This vulnerability needs Unbound to be compiled with DNSCrypt support (\u0027--enable-dnscrypt\u0027) and the \u0027dnscrypt:\u0027 clause to be configured and enabled for the listening interfaces.",
  "published": "2026-07-22T07:17:00Z",
  "severity": "Moderate",
  "cvss": 7.5,
  "cvssVector": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
  "cwe": "Heap-based Buffer Overflow",
  "epss": 0.00293,
  "epssPercentile": 0.22045,
  "priority": "High",
  "priorityTier": 3,
  "exploited": false,
  "vendorExploited": false,
  "disclosed": false,
  "vendorAdvisory": "https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-40691",
  "fixes": [
    {
      "platform": "linux",
      "product": "libunbound2",
      "release": "Ubuntu 18.04.6 LTS (bionic)",
      "fixedVersion": "1.6.7-1ubuntu2.6\u002Besm6",
      "fix": "libunbound2 1.6.7-1ubuntu2.6\u002Besm6",
      "url": "https://patchblox.com/security/fix/linux/ubuntu-bionic-libunbound2-1.6.7-1ubuntu2.6-esm6",
      "released": "2026-09-16T02:17:00Z"
    },
    {
      "platform": "linux",
      "product": "libunbound8",
      "release": "Ubuntu 20.04 LTS (focal)",
      "fixedVersion": "1.9.4-2ubuntu1.11\u002Besm3",
      "fix": "libunbound8 1.9.4-2ubuntu1.11\u002Besm3",
      "url": "https://patchblox.com/security/fix/linux/ubuntu-focal-libunbound8-1.9.4-2ubuntu1.11-esm3",
      "released": "2026-09-16T02:17:00Z"
    },
    {
      "platform": "linux",
      "product": "libunbound8",
      "release": "Ubuntu 22.04.1 LTS (jammy)",
      "fixedVersion": "1.13.1-1ubuntu5.17",
      "fix": "libunbound8 1.13.1-1ubuntu5.17",
      "url": "https://patchblox.com/security/fix/linux/ubuntu-jammy-libunbound8-1.13.1-1ubuntu5.17",
      "released": "2026-09-16T02:17:00Z"
    },
    {
      "platform": "linux",
      "product": "libunbound8",
      "release": "Ubuntu 24.04.5 LTS (noble)",
      "fixedVersion": "1.19.2-1ubuntu3.12",
      "fix": "libunbound8 1.19.2-1ubuntu3.12",
      "url": "https://patchblox.com/security/fix/linux/ubuntu-noble-libunbound8-1.19.2-1ubuntu3.12",
      "released": "2026-09-16T02:17:00Z"
    },
    {
      "platform": "linux",
      "product": "libunbound8",
      "release": "Ubuntu 26.04.1 LTS (resolute)",
      "fixedVersion": "1.24.2-1ubuntu2.4",
      "fix": "libunbound8 1.24.2-1ubuntu2.4",
      "url": "https://patchblox.com/security/fix/linux/ubuntu-resolute-libunbound8-1.24.2-1ubuntu2.4",
      "released": "2026-09-16T02:17:00Z"
    },
    {
      "platform": "linux",
      "product": "python-unbound",
      "release": "Ubuntu 18.04.6 LTS (bionic)",
      "fixedVersion": "1.6.7-1ubuntu2.6\u002Besm6",
      "fix": "python-unbound 1.6.7-1ubuntu2.6\u002Besm6",
      "url": "https://patchblox.com/security/fix/linux/ubuntu-bionic-python-unbound-1.6.7-1ubuntu2.6-esm6",
      "released": "2026-09-16T02:17:00Z"
    },
    {
      "platform": "linux",
      "product": "python-unbound",
      "release": "Ubuntu 20.04 LTS (focal)",
      "fixedVersion": "1.9.4-2ubuntu1.11\u002Besm3",
      "fix": "python-unbound 1.9.4-2ubuntu1.11\u002Besm3",
      "url": "https://patchblox.com/security/fix/linux/ubuntu-focal-python-unbound-1.9.4-2ubuntu1.11-esm3",
      "released": "2026-09-16T02:17:00Z"
    },
    {
      "platform": "linux",
      "product": "python3-unbound",
      "release": "Ubuntu 18.04.6 LTS (bionic)",
      "fixedVersion": "1.6.7-1ubuntu2.6\u002Besm6",
      "fix": "python3-unbound 1.6.7-1ubuntu2.6\u002Besm6",
      "url": "https://patchblox.com/security/fix/linux/ubuntu-bionic-python3-unbound-1.6.7-1ubuntu2.6-esm6",
      "released": "2026-09-16T02:17:00Z"
    },
    {
      "platform": "linux",
      "product": "python3-unbound",
      "release": "Ubuntu 20.04 LTS (focal)",
      "fixedVersion": "1.9.4-2ubuntu1.11\u002Besm3",
      "fix": "python3-unbound 1.9.4-2ubuntu1.11\u002Besm3",
      "url": "https://patchblox.com/security/fix/linux/ubuntu-focal-python3-unbound-1.9.4-2ubuntu1.11-esm3",
      "released": "2026-09-16T02:17:00Z"
    },
    {
      "platform": "linux",
      "product": "python3-unbound",
      "release": "Ubuntu 22.04.1 LTS (jammy)",
      "fixedVersion": "1.13.1-1ubuntu5.17",
      "fix": "python3-unbound 1.13.1-1ubuntu5.17",
      "url": "https://patchblox.com/security/fix/linux/ubuntu-jammy-python3-unbound-1.13.1-1ubuntu5.17",
      "released": "2026-09-16T02:17:00Z"
    },
    {
      "platform": "linux",
      "product": "python3-unbound",
      "release": "Ubuntu 24.04.5 LTS (noble)",
      "fixedVersion": "1.19.2-1ubuntu3.12",
      "fix": "python3-unbound 1.19.2-1ubuntu3.12",
      "url": "https://patchblox.com/security/fix/linux/ubuntu-noble-python3-unbound-1.19.2-1ubuntu3.12",
      "released": "2026-09-16T02:17:00Z"
    },
    {
      "platform": "linux",
      "product": "python3-unbound",
      "release": "Ubuntu 26.04.1 LTS (resolute)",
      "fixedVersion": "1.24.2-1ubuntu2.4",
      "fix": "python3-unbound 1.24.2-1ubuntu2.4",
      "url": "https://patchblox.com/security/fix/linux/ubuntu-resolute-python3-unbound-1.24.2-1ubuntu2.4",
      "released": "2026-09-16T02:17:00Z"
    },
    {
      "platform": "linux",
      "product": "unbound",
      "release": "Debian 13.5 (trixie)",
      "fixedVersion": "1.26.1-0\u002Bdeb13u1",
      "fix": "DEBIAN-CVE-2026-40691",
      "url": "https://patchblox.com/security/fix/linux/debian-cve-2026-40691",
      "released": "2026-07-28T14:13:38Z"
    },
    {
      "platform": "linux",
      "product": "unbound",
      "release": "Debian 14",
      "fixedVersion": "1.25.2-1",
      "fix": "DEBIAN-CVE-2026-40691",
      "url": "https://patchblox.com/security/fix/linux/debian-cve-2026-40691",
      "released": "2026-07-28T14:13:38Z"
    },
    {
      "platform": "linux",
      "product": "unbound",
      "release": "Ubuntu 18.04.6 LTS (bionic)",
      "fixedVersion": "1.6.7-1ubuntu2.6\u002Besm6",
      "fix": "unbound 1.6.7-1ubuntu2.6\u002Besm6",
      "url": "https://patchblox.com/security/fix/linux/ubuntu-bionic-unbound-1.6.7-1ubuntu2.6-esm6",
      "released": "2026-09-16T02:17:00Z"
    },
    {
      "platform": "linux",
      "product": "unbound",
      "release": "Ubuntu 20.04 LTS (focal)",
      "fixedVersion": "1.9.4-2ubuntu1.11\u002Besm3",
      "fix": "unbound 1.9.4-2ubuntu1.11\u002Besm3",
      "url": "https://patchblox.com/security/fix/linux/ubuntu-focal-unbound-1.9.4-2ubuntu1.11-esm3",
      "released": "2026-09-16T02:17:00Z"
    },
    {
      "platform": "linux",
      "product": "unbound",
      "release": "Ubuntu 22.04.1 LTS (jammy)",
      "fixedVersion": "1.13.1-1ubuntu5.17",
      "fix": "unbound 1.13.1-1ubuntu5.17",
      "url": "https://patchblox.com/security/fix/linux/ubuntu-jammy-unbound-1.13.1-1ubuntu5.17",
      "released": "2026-09-16T02:17:00Z"
    },
    {
      "platform": "linux",
      "product": "unbound",
      "release": "Ubuntu 24.04.5 LTS (noble)",
      "fixedVersion": "1.19.2-1ubuntu3.12",
      "fix": "unbound 1.19.2-1ubuntu3.12",
      "url": "https://patchblox.com/security/fix/linux/ubuntu-noble-unbound-1.19.2-1ubuntu3.12",
      "released": "2026-09-16T02:17:00Z"
    },
    {
      "platform": "linux",
      "product": "unbound",
      "release": "Ubuntu 26.04.1 LTS (resolute)",
      "fixedVersion": "1.24.2-1ubuntu2.4",
      "fix": "unbound 1.24.2-1ubuntu2.4",
      "url": "https://patchblox.com/security/fix/linux/ubuntu-resolute-unbound-1.24.2-1ubuntu2.4",
      "released": "2026-09-16T02:17:00Z"
    },
    {
      "platform": "linux",
      "product": "unbound",
      "release": "opensuse-leap 16.0",
      "fixedVersion": "1.25.2-160000.1.1",
      "fix": "OPENSUSE-SU-2026:21550-1",
      "url": "https://patchblox.com/security/fix/linux/opensuse-su-2026-21550-1",
      "released": "2026-08-10T15:27:28Z"
    },
    {
      "platform": "linux",
      "product": "unbound",
      "release": "sles 15.6",
      "fixedVersion": "1.25.2-150600.23.19.1",
      "fix": "SUSE-SU-2026:3885-1",
      "url": "https://patchblox.com/security/fix/linux/suse-su-2026-3885-1",
      "released": "2026-08-31T14:34:37Z"
    },
    {
      "platform": "linux",
      "product": "unbound",
      "release": "sles 15.7",
      "fixedVersion": "1.25.2-150600.23.19.1",
      "fix": "SUSE-SU-2026:3885-1",
      "url": "https://patchblox.com/security/fix/linux/suse-su-2026-3885-1",
      "released": "2026-08-31T14:34:37Z"
    },
    {
      "platform": "linux",
      "product": "unbound",
      "release": "sles 16.0",
      "fixedVersion": "1.25.2-160000.1.1",
      "fix": "SUSE-SU-2026:23226-1",
      "url": "https://patchblox.com/security/fix/linux/suse-su-2026-23226-1",
      "released": "2026-08-10T15:26:22Z"
    },
    {
      "platform": "linux",
      "product": "unbound-anchor",
      "release": "Ubuntu 18.04.6 LTS (bionic)",
      "fixedVersion": "1.6.7-1ubuntu2.6\u002Besm6",
      "fix": "unbound-anchor 1.6.7-1ubuntu2.6\u002Besm6",
      "url": "https://patchblox.com/security/fix/linux/ubuntu-bionic-unbound-anchor-1.6.7-1ubuntu2.6-esm6",
      "released": "2026-09-16T02:17:00Z"
    },
    {
      "platform": "linux",
      "product": "unbound-anchor",
      "release": "Ubuntu 20.04 LTS (focal)",
      "fixedVersion": "1.9.4-2ubuntu1.11\u002Besm3",
      "fix": "unbound-anchor 1.9.4-2ubuntu1.11\u002Besm3",
      "url": "https://patchblox.com/security/fix/linux/ubuntu-focal-unbound-anchor-1.9.4-2ubuntu1.11-esm3",
      "released": "2026-09-16T02:17:00Z"
    },
    {
      "platform": "linux",
      "product": "unbound-anchor",
      "release": "Ubuntu 22.04.1 LTS (jammy)",
      "fixedVersion": "1.13.1-1ubuntu5.17",
      "fix": "unbound-anchor 1.13.1-1ubuntu5.17",
      "url": "https://patchblox.com/security/fix/linux/ubuntu-jammy-unbound-anchor-1.13.1-1ubuntu5.17",
      "released": "2026-09-16T02:17:00Z"
    },
    {
      "platform": "linux",
      "product": "unbound-anchor",
      "release": "Ubuntu 24.04.5 LTS (noble)",
      "fixedVersion": "1.19.2-1ubuntu3.12",
      "fix": "unbound-anchor 1.19.2-1ubuntu3.12",
      "url": "https://patchblox.com/security/fix/linux/ubuntu-noble-unbound-anchor-1.19.2-1ubuntu3.12",
      "released": "2026-09-16T02:17:00Z"
    },
    {
      "platform": "linux",
      "product": "unbound-anchor",
      "release": "Ubuntu 26.04.1 LTS (resolute)",
      "fixedVersion": "1.24.2-1ubuntu2.4",
      "fix": "unbound-anchor 1.24.2-1ubuntu2.4",
      "url": "https://patchblox.com/security/fix/linux/ubuntu-resolute-unbound-anchor-1.24.2-1ubuntu2.4",
      "released": "2026-09-16T02:17:00Z"
    },
    {
      "platform": "linux",
      "product": "unbound-host",
      "release": "Ubuntu 18.04.6 LTS (bionic)",
      "fixedVersion": "1.6.7-1ubuntu2.6\u002Besm6",
      "fix": "unbound-host 1.6.7-1ubuntu2.6\u002Besm6",
      "url": "https://patchblox.com/security/fix/linux/ubuntu-bionic-unbound-host-1.6.7-1ubuntu2.6-esm6",
      "released": "2026-09-16T02:17:00Z"
    },
    {
      "platform": "linux",
      "product": "unbound-host",
      "release": "Ubuntu 20.04 LTS (focal)",
      "fixedVersion": "1.9.4-2ubuntu1.11\u002Besm3",
      "fix": "unbound-host 1.9.4-2ubuntu1.11\u002Besm3",
      "url": "https://patchblox.com/security/fix/linux/ubuntu-focal-unbound-host-1.9.4-2ubuntu1.11-esm3",
      "released": "2026-09-16T02:17:00Z"
    },
    {
      "platform": "linux",
      "product": "unbound-host",
      "release": "Ubuntu 22.04.1 LTS (jammy)",
      "fixedVersion": "1.13.1-1ubuntu5.17",
      "fix": "unbound-host 1.13.1-1ubuntu5.17",
      "url": "https://patchblox.com/security/fix/linux/ubuntu-jammy-unbound-host-1.13.1-1ubuntu5.17",
      "released": "2026-09-16T02:17:00Z"
    },
    {
      "platform": "linux",
      "product": "unbound-host",
      "release": "Ubuntu 24.04.5 LTS (noble)",
      "fixedVersion": "1.19.2-1ubuntu3.12",
      "fix": "unbound-host 1.19.2-1ubuntu3.12",
      "url": "https://patchblox.com/security/fix/linux/ubuntu-noble-unbound-host-1.19.2-1ubuntu3.12",
      "released": "2026-09-16T02:17:00Z"
    },
    {
      "platform": "linux",
      "product": "unbound-host",
      "release": "Ubuntu 26.04.1 LTS (resolute)",
      "fixedVersion": "1.24.2-1ubuntu2.4",
      "fix": "unbound-host 1.24.2-1ubuntu2.4",
      "url": "https://patchblox.com/security/fix/linux/ubuntu-resolute-unbound-host-1.24.2-1ubuntu2.4",
      "released": "2026-09-16T02:17:00Z"
    }
  ],
  "noFixYet": [],
  "dataAsOf": "2026-11-08T13:06:02Z",
  "attribution": {
    "text": "Data: Patchblox Patch Radar",
    "url": "https://patchblox.com/security/patch-radar",
    "terms": "https://patchblox.com/security/patch-radar/use-the-data"
  }
}