{
  "cveId": "CVE-2026-56416",
  "url": "https://patchblox.com/security/cve/CVE-2026-56416",
  "summary": "CVE-2026-56416 is fixed in 12 products on 1 platform, first by DEBIAN-CVE-2026-56416, released July 28, 2026. It is not reported as exploited. Patch Radar priority: Routine.",
  "title": "Possible heap buffer overflow when validator canonicalizes RDATA that contains domain name",
  "description": "In NLnet Labs Unbound up to and including version 1.25.1, when the validator builds the canonical RDATA form for an RRSIG-covered PX/RP/MINFO/SOA RRset, it computes the address of the second embedded domain name as \u0027datstart \u002B dname_valid(datstart, ...)\u0027 and passes it straight to \u0027query_dname_tolower()\u0027 without checking that a second name is actually present in the RDATA. The wire-format parser accepts multi-dname RRs whose RDATA ends after the first name, so an attacker who runs a DNSSEC-signed authoritative server can deliver a record with an absent second domain name (e.g. SOA record) and cause \u0027query_dname_tolower()\u0027 to walk label-by-label through stale bytes in the per-worker \u0027env-\u003Escratch_buffer\u0027, past the end of that heap allocation if \u0027msg-buffer-size\u0027 has been lowered from the default. This leads to heap buffer overflow and on a release build the outcome relies heavily on the contents of the buffer tail and the adjacent heap chunk.",
  "published": "2026-07-22T14:17:22Z",
  "severity": "Moderate",
  "cvss": 4.8,
  "cvssVector": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:L",
  "cwe": "Improper Validation of Integrity Check Value",
  "epss": 0.00124,
  "epssPercentile": 0.02149,
  "priority": "Routine",
  "priorityTier": 4,
  "exploited": false,
  "vendorExploited": false,
  "disclosed": false,
  "vendorAdvisory": "https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-56416",
  "fixes": [
    {
      "platform": "linux",
      "product": "python3-unbound",
      "release": "amzn 2023",
      "fixedVersion": "1.17.1-1.amzn2023.0.13",
      "fix": "ALAS2023-2026-2033",
      "url": "https://patchblox.com/security/fix/linux/alas2023-2026-2033",
      "released": "2026-08-03T09:00:00Z"
    },
    {
      "platform": "linux",
      "product": "python3-unbound-debuginfo",
      "release": "amzn 2023",
      "fixedVersion": "1.17.1-1.amzn2023.0.13",
      "fix": "ALAS2023-2026-2033",
      "url": "https://patchblox.com/security/fix/linux/alas2023-2026-2033",
      "released": "2026-08-03T09:00:00Z"
    },
    {
      "platform": "linux",
      "product": "unbound",
      "release": "Debian 13.5 (trixie)",
      "fixedVersion": "1.26.1-0\u002Bdeb13u1",
      "fix": "DEBIAN-CVE-2026-56416",
      "url": "https://patchblox.com/security/fix/linux/debian-cve-2026-56416",
      "released": "2026-07-28T14:13:38Z"
    },
    {
      "platform": "linux",
      "product": "unbound",
      "release": "Debian 14",
      "fixedVersion": "1.25.2-1",
      "fix": "DEBIAN-CVE-2026-56416",
      "url": "https://patchblox.com/security/fix/linux/debian-cve-2026-56416",
      "released": "2026-07-28T14:13:38Z"
    },
    {
      "platform": "linux",
      "product": "unbound",
      "release": "amzn 2023",
      "fixedVersion": "1.17.1-1.amzn2023.0.13",
      "fix": "ALAS2023-2026-2033",
      "url": "https://patchblox.com/security/fix/linux/alas2023-2026-2033",
      "released": "2026-08-03T09:00:00Z"
    },
    {
      "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": "amzn 2023",
      "fixedVersion": "1.17.1-1.amzn2023.0.13",
      "fix": "ALAS2023-2026-2033",
      "url": "https://patchblox.com/security/fix/linux/alas2023-2026-2033",
      "released": "2026-08-03T09:00:00Z"
    },
    {
      "platform": "linux",
      "product": "unbound-anchor-debuginfo",
      "release": "amzn 2023",
      "fixedVersion": "1.17.1-1.amzn2023.0.13",
      "fix": "ALAS2023-2026-2033",
      "url": "https://patchblox.com/security/fix/linux/alas2023-2026-2033",
      "released": "2026-08-03T09:00:00Z"
    },
    {
      "platform": "linux",
      "product": "unbound-debuginfo",
      "release": "amzn 2023",
      "fixedVersion": "1.17.1-1.amzn2023.0.13",
      "fix": "ALAS2023-2026-2033",
      "url": "https://patchblox.com/security/fix/linux/alas2023-2026-2033",
      "released": "2026-08-03T09:00:00Z"
    },
    {
      "platform": "linux",
      "product": "unbound-debugsource",
      "release": "amzn 2023",
      "fixedVersion": "1.17.1-1.amzn2023.0.13",
      "fix": "ALAS2023-2026-2033",
      "url": "https://patchblox.com/security/fix/linux/alas2023-2026-2033",
      "released": "2026-08-03T09:00:00Z"
    },
    {
      "platform": "linux",
      "product": "unbound-devel",
      "release": "amzn 2023",
      "fixedVersion": "1.17.1-1.amzn2023.0.13",
      "fix": "ALAS2023-2026-2033",
      "url": "https://patchblox.com/security/fix/linux/alas2023-2026-2033",
      "released": "2026-08-03T09:00:00Z"
    },
    {
      "platform": "linux",
      "product": "unbound-libs",
      "release": "amzn 2023",
      "fixedVersion": "1.17.1-1.amzn2023.0.13",
      "fix": "ALAS2023-2026-2033",
      "url": "https://patchblox.com/security/fix/linux/alas2023-2026-2033",
      "released": "2026-08-03T09:00:00Z"
    },
    {
      "platform": "linux",
      "product": "unbound-libs-debuginfo",
      "release": "amzn 2023",
      "fixedVersion": "1.17.1-1.amzn2023.0.13",
      "fix": "ALAS2023-2026-2033",
      "url": "https://patchblox.com/security/fix/linux/alas2023-2026-2033",
      "released": "2026-08-03T09:00:00Z"
    },
    {
      "platform": "linux",
      "product": "unbound-utils",
      "release": "amzn 2023",
      "fixedVersion": "1.17.1-1.amzn2023.0.13",
      "fix": "ALAS2023-2026-2033",
      "url": "https://patchblox.com/security/fix/linux/alas2023-2026-2033",
      "released": "2026-08-03T09:00:00Z"
    },
    {
      "platform": "linux",
      "product": "unbound-utils-debuginfo",
      "release": "amzn 2023",
      "fixedVersion": "1.17.1-1.amzn2023.0.13",
      "fix": "ALAS2023-2026-2033",
      "url": "https://patchblox.com/security/fix/linux/alas2023-2026-2033",
      "released": "2026-08-03T09:00:00Z"
    }
  ],
  "noFixYet": [],
  "dataAsOf": "2026-11-09T13:31:49Z",
  "attribution": {
    "text": "Data: Patchblox Patch Radar",
    "url": "https://patchblox.com/security/patch-radar",
    "terms": "https://patchblox.com/security/patch-radar/use-the-data"
  }
}