ubuntu-cve-2026-33278
Vulnerability from osv_ubuntu
Published
2026-05-20 00:00
Modified
2026-06-30 16:20
Summary
Details

NLnet Labs Unbound 1.19.1 up to and including version 1.25.0 has a vulnerability in the DNSSEC validator that enables denial of service and possible remote code execution as a result of deep copying a data structure and erroneously overwriting a destination pointer. An adversary can exploit the vulnerability by controlling a malicious signed zone and querying a vulnerable Unbound. When DS sub-queries need to suspend validation due to NSEC3 computational budget exhaustion (introduced in Unbound 1.19.1), Unbound deep-copies response messages to preserve them across memory region teardown. A struct-assignment bug overwrites the destination's pointer with the source's pointer. After the sub-query region is freed, the resumed validator dereferences this dangling pointer, triggering a crash or potentially enabling arbitrary code execution. Unbound 1.25.1 contains a patch with a fix to preserve the correct pointer when deep copying the data structure.

Severity
9.1 (Critical)
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H/E:U/U:Red
8.1 (High)
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
9.8 (Critical)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
N/A (UNKNOWN)
high
References
To clipboard 

{
  "affected": [
    {
      "ecosystem_specific": {
        "availability": "No subscription required",
        "binaries": [
          {
            "binary_name": "libunbound8",
            "binary_version": "1.19.2-1ubuntu3.8"
          },
          {
            "binary_name": "python3-unbound",
            "binary_version": "1.19.2-1ubuntu3.8"
          },
          {
            "binary_name": "unbound",
            "binary_version": "1.19.2-1ubuntu3.8"
          },
          {
            "binary_name": "unbound-anchor",
            "binary_version": "1.19.2-1ubuntu3.8"
          },
          {
            "binary_name": "unbound-host",
            "binary_version": "1.19.2-1ubuntu3.8"
          }
        ],
        "priority_reason": "Possible remote code execution"
      },
      "package": {
        "ecosystem": "Ubuntu:24.04:LTS",
        "name": "unbound",
        "purl": "pkg:deb/ubuntu/unbound@1.19.2-1ubuntu3.8?arch=source\u0026distro=noble"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "1.19.2-1ubuntu3.8"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "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"
      ]
    },
    {
      "ecosystem_specific": {
        "availability": "No subscription required",
        "binaries": [
          {
            "binary_name": "libunbound8",
            "binary_version": "1.22.0-2ubuntu2.3"
          },
          {
            "binary_name": "python3-unbound",
            "binary_version": "1.22.0-2ubuntu2.3"
          },
          {
            "binary_name": "unbound",
            "binary_version": "1.22.0-2ubuntu2.3"
          },
          {
            "binary_name": "unbound-anchor",
            "binary_version": "1.22.0-2ubuntu2.3"
          },
          {
            "binary_name": "unbound-host",
            "binary_version": "1.22.0-2ubuntu2.3"
          }
        ],
        "priority_reason": "Possible remote code execution"
      },
      "package": {
        "ecosystem": "Ubuntu:25.10",
        "name": "unbound",
        "purl": "pkg:deb/ubuntu/unbound@1.22.0-2ubuntu2.3?arch=source\u0026distro=questing"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "1.22.0-2ubuntu2.3"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "1.22.0-1ubuntu1",
        "1.22.0-2ubuntu1",
        "1.22.0-2ubuntu2",
        "1.22.0-2ubuntu2.1",
        "1.22.0-2ubuntu2.2"
      ]
    },
    {
      "ecosystem_specific": {
        "availability": "No subscription required",
        "binaries": [
          {
            "binary_name": "libunbound8",
            "binary_version": "1.24.2-1ubuntu2.1"
          },
          {
            "binary_name": "python3-unbound",
            "binary_version": "1.24.2-1ubuntu2.1"
          },
          {
            "binary_name": "unbound",
            "binary_version": "1.24.2-1ubuntu2.1"
          },
          {
            "binary_name": "unbound-anchor",
            "binary_version": "1.24.2-1ubuntu2.1"
          },
          {
            "binary_name": "unbound-host",
            "binary_version": "1.24.2-1ubuntu2.1"
          }
        ],
        "priority_reason": "Possible remote code execution"
      },
      "package": {
        "ecosystem": "Ubuntu:26.04:LTS",
        "name": "unbound",
        "purl": "pkg:deb/ubuntu/unbound@1.24.2-1ubuntu2.1?arch=source\u0026distro=resolute"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "1.24.2-1ubuntu2.1"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "1.22.0-2ubuntu2",
        "1.22.0-2ubuntu4",
        "1.24.2-1ubuntu1",
        "1.24.2-1ubuntu2"
      ]
    }
  ],
  "aliases": [],
  "details": "NLnet Labs Unbound 1.19.1 up to and including version 1.25.0 has a vulnerability in the DNSSEC validator that enables denial of service and possible remote code execution as a result of deep copying a data structure and erroneously overwriting a destination pointer. An adversary can exploit the vulnerability by controlling a malicious signed zone and querying a vulnerable Unbound. When DS sub-queries need to suspend validation due to NSEC3 computational budget exhaustion (introduced in Unbound 1.19.1), Unbound deep-copies response messages to preserve them across memory region teardown. A struct-assignment bug overwrites the destination\u0027s pointer with the source\u0027s pointer. After the sub-query region is freed, the resumed validator dereferences this dangling pointer, triggering a crash or potentially enabling arbitrary code execution. Unbound 1.25.1 contains a patch with a fix to preserve the correct pointer when deep copying the data structure.",
  "id": "UBUNTU-CVE-2026-33278",
  "modified": "2026-06-30T16:20:55Z",
  "published": "2026-05-20T00:00:00Z",
  "references": [
    {
      "type": "REPORT",
      "url": "https://ubuntu.com/security/CVE-2026-33278"
    },
    {
      "type": "REPORT",
      "url": "https://www.cve.org/CVERecord?id=CVE-2026-33278"
    },
    {
      "type": "REPORT",
      "url": "https://nlnetlabs.nl/news/2026/May/20/unbound-1.25.1-released/"
    },
    {
      "type": "ADVISORY",
      "url": "https://ubuntu.com/security/notices/USN-8282-1"
    }
  ],
  "related": [
    "USN-8282-1"
  ],
  "schema_version": "1.7.0",
  "severity": [
    {
      "score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H/E:U/U:Red",
      "type": "CVSS_V4"
    },
    {
      "score": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H",
      "type": "CVSS_V3"
    },
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
      "type": "CVSS_V3"
    },
    {
      "score": "high",
      "type": "Ubuntu"
    }
  ],
  "upstream": [
    "CVE-2026-33278"
  ]
}



Log in or create an account to share your comment.




Tags
Taxonomy of the tags.





Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

Sightings

Author Source Type Date Other

Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
  • Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
  • Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
  • Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
  • Not confirmed: The user expressed doubt about the validity of the vulnerability.
  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.


Detection rules are retrieved from Rulezet.