CVE catalog

CVE-2026-56416

In NLnet Labs Unbound up to and including version…

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 'datstart + dname_valid(datstart, ...)' and passes it straight to 'query_dname_tolower()' 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 'query_dname_tolower()' to walk label-by-label through stale bytes in the per-worker 'env->scratch_buffer', past the end of that heap allocation if 'msg-buffer-size' 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.

Severity: Medium · CVSS 5.6CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:L
Published: Jul 22, 2026, 1:10:24 PM UTC
Source: [NVD] · [CVE record]
EPSS: 0.12% · Oct 27, 2026

Projects and upstream resources

[unbound][Source-reported homepage]

Reported versions and fixes

Each observation applies to its named package, distribution, and release. Distribution backports can fix a vulnerability while retaining an older upstream version number.

Version impact has not been established. The original provider fields are retained below.

Provider details and historical evidence

Original provider fields

{
  "package_releases": [
    {
      "name": "unbound",
      "status": "fixed",
      "release": "sid",
      "version": "1.26.2-1"
    },
    {
      "name": "unbound",
      "status": "fixed",
      "release": "forky",
      "version": "1.26.2-1"
    },
    {
      "name": "unbound",
      "status": "vulnerable",
      "release": "trixie",
      "version": "1.22.0-2+deb13u3"
    },
    {
      "name": "unbound",
      "status": "fixed",
      "release": "trixie-security",
      "version": "1.26.2-0+deb13u1"
    },
    {
      "name": "unbound",
      "status": "vulnerable",
      "release": "bookworm",
      "version": "1.17.1-2+deb12u4"
    },
    {
      "name": "unbound",
      "status": "vulnerable",
      "release": "bookworm-security",
      "version": "1.17.1-2+deb12u3"
    }
  ],
  "fixed_versions": [
    {
      "bug": null,
      "name": "unbound",
      "type": "source",
      "origin": null,
      "release": "sid",
      "urgency": "not yet assigned",
      "fixed_version": "1.25.2-1"
    },
    {
      "bug": null,
      "name": "unbound",
      "type": "source",
      "origin": null,
      "release": "forky",
      "urgency": "not yet assigned",
      "fixed_version": "1.25.2-1"
    },
    {
      "bug": null,
      "name": "unbound",
      "type": "source",
      "origin": null,
      "release": "trixie",
      "urgency": "not yet assigned",
      "fixed_version": "1.26.1-0+deb13u1"
    },
    {
      "bug": null,
      "name": "unbound",
      "type": "source",
      "origin": null,
      "release": "bookworm",
      "urgency": "not yet assigned",
      "fixed_version": ""
    }
  ],
  "distribution_packages": [
    {
      "name": "unbound",
      "distro": "alpine",
      "ranges": [
        {
          "type": "ECOSYSTEM",
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "1.25.2-r0"
            }
          ]
        }
      ],
      "release": "3.22",
      "versions": [],
      "ecosystem": "apk",
      "fixed_version": "1.25.2-r0",
      "provider_record_id": "ALPINE-CVE-2026-56416"
    },
    {
      "name": "unbound",
      "distro": "alpine",
      "ranges": [
        {
          "type": "ECOSYSTEM",
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "1.25.2-r0"
            }
          ]
        }
      ],
      "release": "3.23",
      "versions": [],
      "ecosystem": "apk",
      "fixed_version": "1.25.2-r0",
      "provider_record_id": "ALPINE-CVE-2026-56416"
    },
    {
      "name": "unbound",
      "distro": "alpine",
      "ranges": [
        {
          "type": "ECOSYSTEM",
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "1.25.2-r0"
            }
          ]
        }
      ],
      "release": "3.24",
      "versions": [],
      "ecosystem": "apk",
      "fixed_version": "1.25.2-r0",
      "provider_record_id": "ALPINE-CVE-2026-56416"
    },
    {
      "name": "unbound",
      "distro": "ubuntu",
      "ranges": [
        {
          "type": "ECOSYSTEM",
          "events": [
            {
              "introduced": "0"
            }
          ]
        }
      ],
      "release": "pro",
      "versions": [
        "1.9.0-2ubuntu1",
        "1.9.0-2ubuntu2",
        "1.9.4-2",
        "1.9.4-2ubuntu1",
        "1.9.4-2ubuntu1.1",
        "1.9.4-2ubuntu1.2",
        "1.9.4-2ubuntu1.3",
        "1.9.4-2ubuntu1.4",
        "1.9.4-2ubuntu1.5",
        "1.9.4-2ubuntu1.6",
        "1.9.4-2ubuntu1.8",
        "1.9.4-2ubuntu1.9",
        "1.9.4-2ubuntu1.11",
        "1.9.4-2ubuntu1.11+esm1",
        "1.9.4-2ubuntu1.11+esm2",
        "1.9.4-2ubuntu1.11+esm3"
      ],
      "ecosystem": "deb",
      "fixed_version": "",
      "provider_record_id": "UBUNTU-CVE-2026-56416"
    },
    {
      "name": "unbound",
      "distro": "ubuntu",
      "ranges": [
        {
          "type": "ECOSYSTEM",
          "events": [
            {
              "introduced": "0"
            }
          ]
        }
      ],
      "release": "22.04",
      "versions": [
        "1.13.1-1ubuntu1",
        "1.13.1-1ubuntu3",
        "1.13.1-1ubuntu5",
        "1.13.1-1ubuntu5.1",
        "1.13.1-1ubuntu5.2",
        "1.13.1-1ubuntu5.3",
        "1.13.1-1ubuntu5.4",
        "1.13.1-1ubuntu5.5",
        "1.13.1-1ubuntu5.7",
        "1.13.1-1ubuntu5.8",
        "1.13.1-1ubuntu5.10",
        "1.13.1-1ubuntu5.11",
        "1.13.1-1ubuntu5.12",
        "1.13.1-1ubuntu5.13",
        "1.13.1-1ubuntu5.14",
        "1.13.1-1ubuntu5.15",
        "1.13.1-1ubuntu5.16",
        "1.13.1-1ubuntu5.17"
      ],
      "ecosystem": "deb",
      "fixed_version": "",
      "provider_record_id": "UBUNTU-CVE-2026-56416"
    },
    {
      "name": "unbound",
      "distro": "ubuntu",
      "ranges": [
        {
          "type": "ECOSYSTEM",
          "events": [
            {
              "introduced": "0"
            }
          ]
        }
      ],
      "release": "24.04",
      "versions": [
        "1.17.1-2",
        "1.18.0-2ubuntu1",
        "1.18.0-2ubuntu2",
        "1.19.1-1ubuntu1",
        "1.19.2-1ubuntu1",
        "1.19.2-1ubuntu3",
        "1.19.2-1ubuntu3.1",
        "1.19.2-1ubuntu3.2",
        "1.19.2-1ubuntu3.3",
        "1.19.2-1ubuntu3.4",
        "1.19.2-1ubuntu3.5",
        "1.19.2-1ubuntu3.6",
        "1.19.2-1ubuntu3.7",
        "1.19.2-1ubuntu3.8",
        "1.19.2-1ubuntu3.9",
        "1.19.2-1ubuntu3.10",
        "1.19.2-1ubuntu3.12"
      ],
      "ecosystem": "deb",
      "fixed_version": "",
      "provider_record_id": "UBUNTU-CVE-2026-56416"
    },
    {
      "name": "unbound",
      "distro": "ubuntu",
      "ranges": [
        {
          "type": "ECOSYSTEM",
          "events": [
            {
              "introduced": "0"
            }
          ]
        }
      ],
      "release": "26.10",
      "versions": [
        "1.24.2-1ubuntu2",
        "1.25.1-1ubuntu1",
        "1.25.1-1ubuntu3"
      ],
      "ecosystem": "deb",
      "fixed_version": "",
      "provider_record_id": "UBUNTU-CVE-2026-56416"
    },
    {
      "name": "unbound",
      "distro": "ubuntu",
      "ranges": [
        {
          "type": "ECOSYSTEM",
          "events": [
            {
              "introduced": "0"
            }
          ]
        }
      ],
      "release": "26.04",
      "versions": [
        "1.22.0-2ubuntu2",
        "1.22.0-2ubuntu4",
        "1.24.2-1ubuntu1",
        "1.24.2-1ubuntu2",
        "1.24.2-1ubuntu2.1",
        "1.24.2-1ubuntu2.2",
        "1.24.2-1ubuntu2.3",
        "1.24.2-1ubuntu2.4"
      ],
      "ecosystem": "deb",
      "fixed_version": "",
      "provider_record_id": "UBUNTU-CVE-2026-56416"
    },
    {
      "name": "unbound",
      "ranges": [
        {
          "fixed": "1.25.2",
          "introduced": "",
          "last_affected": "",
          "start_excluding": ""
        }
      ],
      "ecosystem": "cpe",
      "fixed_version": "1.25.2",
      "provider_record_id": "NVD-CVE-2026-56416"
    }
  ]
}

OpenFactory catalog packages

Matching against OpenFactory catalog package versions is in progress.

[Debian 12 (Bookworm)]

[libunbound8]Unknown
Source package: [unbound]
Details (4)
- 1.17.1-2+deb12u4 · amd64 · bookworm
  Affected
  nvd · unbound · debian · bookworm; nvd · unbound · debian · 12
- 1.17.1-2+deb12u4 · arm64 · bookworm
  Affected
  nvd · unbound · debian · bookworm; nvd · unbound · debian · 12
- 1.17.1-2+deb12u3 · amd64 · bookworm-security
  Affected
  nvd · unbound · debian · bookworm; nvd · unbound · debian · 12
- 1.17.1-2+deb12u3 · arm64 · bookworm-security
  Affected
  nvd · unbound · debian · bookworm; nvd · unbound · debian · 12
[libunbound-dev]Unknown
Source package: [unbound]
Details (4)
- 1.17.1-2+deb12u4 · amd64 · bookworm
  Affected
  nvd · unbound · debian · bookworm; nvd · unbound · debian · 12
- 1.17.1-2+deb12u4 · arm64 · bookworm
  Affected
  nvd · unbound · debian · bookworm; nvd · unbound · debian · 12
- 1.17.1-2+deb12u3 · amd64 · bookworm-security
  Affected
  nvd · unbound · debian · bookworm; nvd · unbound · debian · 12
- 1.17.1-2+deb12u3 · arm64 · bookworm-security
  Affected
  nvd · unbound · debian · bookworm; nvd · unbound · debian · 12
[python3-unbound]Unknown
Source package: [unbound]
Details (4)
- 1.17.1-2+deb12u4 · amd64 · bookworm
  Affected
  nvd · unbound · debian · bookworm; nvd · unbound · debian · 12
- 1.17.1-2+deb12u4 · arm64 · bookworm
  Affected
  nvd · unbound · debian · bookworm; nvd · unbound · debian · 12
- 1.17.1-2+deb12u3 · amd64 · bookworm-security
  Affected
  nvd · unbound · debian · bookworm; nvd · unbound · debian · 12
- 1.17.1-2+deb12u3 · arm64 · bookworm-security
  Affected
  nvd · unbound · debian · bookworm; nvd · unbound · debian · 12
[unbound]Unknown
Details (4)
- 1.17.1-2+deb12u4 · amd64 · bookworm
  Affected
  nvd · unbound · debian · bookworm; nvd · unbound · debian · 12
- 1.17.1-2+deb12u4 · arm64 · bookworm
  Affected
  nvd · unbound · debian · bookworm; nvd · unbound · debian · 12
- 1.17.1-2+deb12u3 · amd64 · bookworm-security
  Affected
  nvd · unbound · debian · bookworm; nvd · unbound · debian · 12
- 1.17.1-2+deb12u3 · arm64 · bookworm-security
  Affected
  nvd · unbound · debian · bookworm; nvd · unbound · debian · 12
[unbound-anchor]Unknown
Source package: [unbound]
Details (4)
- 1.17.1-2+deb12u4 · amd64 · bookworm
  Affected
  nvd · unbound · debian · bookworm; nvd · unbound · debian · 12
- 1.17.1-2+deb12u4 · arm64 · bookworm
  Affected
  nvd · unbound · debian · bookworm; nvd · unbound · debian · 12
- 1.17.1-2+deb12u3 · amd64 · bookworm-security
  Affected
  nvd · unbound · debian · bookworm; nvd · unbound · debian · 12
- 1.17.1-2+deb12u3 · arm64 · bookworm-security
  Affected
  nvd · unbound · debian · bookworm; nvd · unbound · debian · 12
[unbound-host]Unknown
Source package: [unbound]
Details (4)
- 1.17.1-2+deb12u4 · amd64 · bookworm
  Affected
  nvd · unbound · debian · bookworm; nvd · unbound · debian · 12
- 1.17.1-2+deb12u4 · arm64 · bookworm
  Affected
  nvd · unbound · debian · bookworm; nvd · unbound · debian · 12
- 1.17.1-2+deb12u3 · amd64 · bookworm-security
  Affected
  nvd · unbound · debian · bookworm; nvd · unbound · debian · 12
- 1.17.1-2+deb12u3 · arm64 · bookworm-security
  Affected
  nvd · unbound · debian · bookworm; nvd · unbound · debian · 12

[Debian 13 (Trixie)]

[libunbound8]Unknown
Source package: [unbound]
Details (6)
- 1.22.0-2+deb13u3 · amd64 · trixie
  Affected · Fixed: 1.26.1-0+deb13u1
  nvd · unbound · debian · 13
- 1.22.0-2+deb13u3 · arm64 · trixie
  Affected · Fixed: 1.26.1-0+deb13u1
  nvd · unbound · debian · 13
- 1.22.0-2+deb13u3 · amd64 · trixie-security · Historical version
  Affected · Fixed: 1.26.1-0+deb13u1
  nvd · unbound · debian · 13
- 1.22.0-2+deb13u3 · arm64 · trixie-security
  Affected · Fixed: 1.26.1-0+deb13u1
  nvd · unbound · debian · 13
- 1.26.1-0+deb13u1 · amd64 · trixie-security · Historical version
  Fixed · Fixed: 1.26.1-0+deb13u1
  nvd · unbound · debian · 13
- 1.26.2-0+deb13u1 · amd64 · trixie-security
  Fixed · Fixed: 1.26.1-0+deb13u1
  nvd · unbound · debian · 13
[libunbound-dev]Unknown
Source package: [unbound]
Details (6)
- 1.22.0-2+deb13u3 · amd64 · trixie
  Affected · Fixed: 1.26.1-0+deb13u1
  nvd · unbound · debian · 13
- 1.22.0-2+deb13u3 · arm64 · trixie
  Affected · Fixed: 1.26.1-0+deb13u1
  nvd · unbound · debian · 13
- 1.22.0-2+deb13u3 · amd64 · trixie-security · Historical version
  Affected · Fixed: 1.26.1-0+deb13u1
  nvd · unbound · debian · 13
- 1.22.0-2+deb13u3 · arm64 · trixie-security
  Affected · Fixed: 1.26.1-0+deb13u1
  nvd · unbound · debian · 13
- 1.26.1-0+deb13u1 · amd64 · trixie-security · Historical version
  Fixed · Fixed: 1.26.1-0+deb13u1
  nvd · unbound · debian · 13
- 1.26.2-0+deb13u1 · amd64 · trixie-security
  Fixed · Fixed: 1.26.1-0+deb13u1
  nvd · unbound · debian · 13
[python3-unbound]Unknown
Source package: [unbound]
Details (6)
- 1.22.0-2+deb13u3 · amd64 · trixie
  Affected · Fixed: 1.26.1-0+deb13u1
  nvd · unbound · debian · 13
- 1.22.0-2+deb13u3 · arm64 · trixie
  Affected · Fixed: 1.26.1-0+deb13u1
  nvd · unbound · debian · 13
- 1.22.0-2+deb13u3 · amd64 · trixie-security · Historical version
  Affected · Fixed: 1.26.1-0+deb13u1
  nvd · unbound · debian · 13
- 1.22.0-2+deb13u3 · arm64 · trixie-security
  Affected · Fixed: 1.26.1-0+deb13u1
  nvd · unbound · debian · 13
- 1.26.1-0+deb13u1 · amd64 · trixie-security · Historical version
  Fixed · Fixed: 1.26.1-0+deb13u1
  nvd · unbound · debian · 13
- 1.26.2-0+deb13u1 · amd64 · trixie-security
  Fixed · Fixed: 1.26.1-0+deb13u1
  nvd · unbound · debian · 13
[unbound]Unknown
Details (6)
- 1.22.0-2+deb13u3 · amd64 · trixie
  Affected · Fixed: 1.26.1-0+deb13u1
  nvd · unbound · debian · 13
- 1.22.0-2+deb13u3 · arm64 · trixie
  Affected · Fixed: 1.26.1-0+deb13u1
  nvd · unbound · debian · 13
- 1.22.0-2+deb13u3 · amd64 · trixie-security · Historical version
  Affected · Fixed: 1.26.1-0+deb13u1
  nvd · unbound · debian · 13
- 1.22.0-2+deb13u3 · arm64 · trixie-security
  Affected · Fixed: 1.26.1-0+deb13u1
  nvd · unbound · debian · 13
- 1.26.1-0+deb13u1 · amd64 · trixie-security · Historical version
  Fixed · Fixed: 1.26.1-0+deb13u1
  nvd · unbound · debian · 13
- 1.26.2-0+deb13u1 · amd64 · trixie-security
  Fixed · Fixed: 1.26.1-0+deb13u1
  nvd · unbound · debian · 13
[unbound-anchor]Unknown
Source package: [unbound]
Details (6)
- 1.22.0-2+deb13u3 · amd64 · trixie
  Affected · Fixed: 1.26.1-0+deb13u1
  nvd · unbound · debian · 13
- 1.22.0-2+deb13u3 · arm64 · trixie
  Affected · Fixed: 1.26.1-0+deb13u1
  nvd · unbound · debian · 13
- 1.22.0-2+deb13u3 · amd64 · trixie-security · Historical version
  Affected · Fixed: 1.26.1-0+deb13u1
  nvd · unbound · debian · 13
- 1.22.0-2+deb13u3 · arm64 · trixie-security
  Affected · Fixed: 1.26.1-0+deb13u1
  nvd · unbound · debian · 13
- 1.26.1-0+deb13u1 · amd64 · trixie-security · Historical version
  Fixed · Fixed: 1.26.1-0+deb13u1
  nvd · unbound · debian · 13
- 1.26.2-0+deb13u1 · amd64 · trixie-security
  Fixed · Fixed: 1.26.1-0+deb13u1
  nvd · unbound · debian · 13
[unbound-host]Unknown
Source package: [unbound]
Details (6)
- 1.22.0-2+deb13u3 · amd64 · trixie
  Affected · Fixed: 1.26.1-0+deb13u1
  nvd · unbound · debian · 13
- 1.22.0-2+deb13u3 · arm64 · trixie
  Affected · Fixed: 1.26.1-0+deb13u1
  nvd · unbound · debian · 13
- 1.22.0-2+deb13u3 · amd64 · trixie-security · Historical version
  Affected · Fixed: 1.26.1-0+deb13u1
  nvd · unbound · debian · 13
- 1.22.0-2+deb13u3 · arm64 · trixie-security
  Affected · Fixed: 1.26.1-0+deb13u1
  nvd · unbound · debian · 13
- 1.26.1-0+deb13u1 · amd64 · trixie-security · Historical version
  Fixed · Fixed: 1.26.1-0+deb13u1
  nvd · unbound · debian · 13
- 1.26.2-0+deb13u1 · amd64 · trixie-security
  Fixed · Fixed: 1.26.1-0+deb13u1
  nvd · unbound · debian · 13

Observed: Oct 27, 2026, 7:12:09 AM UTC

References

[CERT-Bund public advisories] · [Debian Security Tracker] · [FIRST EPSS] · [National Vulnerability Database (NVD)] · [OSV Package Vulnerability Database] · [Red Hat security advisories and VEX] · [SUSE security advisories and VEX]