MediumFix available

dnsmasq — security advisory

Type: advisorySources: OSVAdvisory ID: DEBIAN-CVE-2020-25687

A flaw was found in dnsmasq before version 2.83. A heap-based buffer overflow was discovered in dnsmasq when DNSSEC is enabled and before it validates the received DNS entries. This flaw allows a remote attacker, who can create valid DNS replies, to cause an overflow in a heap-allocated memory. This flaw is caused by the lack of length checks in rfc1035.c:extract_name(), which could be abused to make the code execute memcpy() with a negative size in sort_rrset() and cause a crash in dnsmasq, resulting in a denial of service. The highest threat from this vulnerability is to system availability.

Products: dnsmasq
Affected versions: Not specified
Fixed versions: 2.83-1
CVEs: CVE-2020-25687
Confirmed fixed CVEs: Not specified
Updated in this feed: 1 Nov 2026, 13:29 UTC · Revision 1

Source evidence

DEBIAN-CVE-2020-25687

core-osv · Original source

Published 20 Jan 2021, 17:15 UTC

osv:DEBIAN-CVE-2020-25687

dnsmasq

Fixed versions: 2.83-1

dnsmasq

Fixed versions: 2.83-1

dnsmasq

Fixed versions: 2.83-1

Complete source record

{
  "id": "f43758b5c17566efd4b791ffcb27ecc33df2d1e0e1ef7cb9787e8a563227ffa9",
  "url": "https://osv.dev/vulnerability/DEBIAN-CVE-2020-25687",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "DEBIAN-CVE-2020-25687",
    "summary": "A flaw was found in dnsmasq before version 2.83. A heap-based buffer overflow was discovered in dnsmasq when DNSSEC is enabled and before it validates the received DNS entries. This flaw allows a remote attacker, who can create valid DNS replies, to cause an overflow in a heap-allocated memory. This flaw is caused by the lack of length checks in rfc1035.c:extract_name(), which could be abused to make the code execute memcpy() with a negative size in sort_rrset() and cause a crash in dnsmasq, resulting in a denial of service. The highest threat from this vulnerability is to system availability.",
    "evidence": "osv:DEBIAN-CVE-2020-25687",
    "products": [
      {
        "name": {
          "value": "dnsmasq",
          "evidence": "/affected/0/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [
          {
            "value": "2.83-1",
            "evidence": "/affected/0/ranges"
          }
        ],
        "affected_versions": []
      },
      {
        "name": {
          "value": "dnsmasq",
          "evidence": "/affected/1/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [
          {
            "value": "2.83-1",
            "evidence": "/affected/1/ranges"
          }
        ],
        "affected_versions": []
      },
      {
        "name": {
          "value": "dnsmasq",
          "evidence": "/affected/2/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [
          {
            "value": "2.83-1",
            "evidence": "/affected/2/ranges"
          }
        ],
        "affected_versions": []
      }
    ],
    "severity": "medium",
    "structured": {
      "id": "DEBIAN-CVE-2020-25687",
      "aliases": [
        "DEBIAN-CVE-2020-25687"
      ],
      "metrics": [
        {
          "type": "CVSS_V3",
          "score": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H"
        }
      ],
      "affected": [
        {
          "ranges": [
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "0"
                },
                {
                  "fixed": "2.83-1"
                }
              ]
            }
          ],
          "package": {
            "name": "dnsmasq",
            "purl": "pkg:deb/debian/dnsmasq?arch=source&distro=bookworm",
            "ecosystem": "Debian:12"
          },
          "database_specific": {
            "source": "https://storage.googleapis.com/debian-osv/debian-cve-osv/DEBIAN-CVE-2020-25687.json"
          },
          "ecosystem_specific": {
            "urgency": "not yet assigned"
          }
        },
        {
          "ranges": [
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "0"
                },
                {
                  "fixed": "2.83-1"
                }
              ]
            }
          ],
          "package": {
            "name": "dnsmasq",
            "purl": "pkg:deb/debian/dnsmasq?arch=source&distro=trixie",
            "ecosystem": "Debian:13"
          },
          "database_specific": {
            "source": "https://storage.googleapis.com/debian-osv/debian-cve-osv/DEBIAN-CVE-2020-25687.json"
          },
          "ecosystem_specific": {
            "urgency": "not yet assigned"
          }
        },
        {
          "ranges": [
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "0"
                },
                {
                  "fixed": "2.83-1"
                }
              ]
            }
          ],
          "package": {
            "name": "dnsmasq",
            "purl": "pkg:deb/debian/dnsmasq?arch=source&distro=forky",
            "ecosystem": "Debian:14"
          },
          "database_specific": {
            "source": "https://storage.googleapis.com/debian-osv/debian-cve-osv/DEBIAN-CVE-2020-25687.json"
          },
          "ecosystem_specific": {
            "urgency": "not yet assigned"
          }
        }
      ],
      "modified": "2026-10-26T12:02:30.780733771Z",
      "provider": "osv",
      "upstream": [
        "CVE-2020-25687"
      ],
      "references": [
        "https://security-tracker.debian.org/tracker/CVE-2020-25687"
      ]
    },
    "related_cves": [
      {
        "value": "CVE-2020-25687",
        "evidence": "/upstream"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 452402,
  "published_at": "2021-01-20T17:15:13.06+00:00"
}