libevent — security advisory

{
  "id": "e8a433c431b8bee4e9b91f381ba80bb3ddad0c6d3ef0b1d40d300d0c879e4c09",
  "url": "https://osv.dev/vulnerability/DEBIAN-CVE-2026-63387",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "DEBIAN-CVE-2026-63387",
    "summary": "Libevent is an event notification library. Prior to 2.1.13 and 2.2.2-alpha, libevent has an off-by-one stack buffer overflow in evdns.c when dnsname_to_labels formats a name-bearing DNS record at the end of the 64 KB stack buffer allocated by evdns_server_request_format_response. The final-label check permits j plus label_len plus one to equal buf_len, after which the terminating null byte is written to buf[buf_len]. A crafted DNS server response containing PTR, CNAME, MX, NS, or SOA data can trigger the one-byte out-of-bounds write and crash or corrupt the process. This issue is fixed in versions 2.1.13 and 2.2.2-alpha.",
    "evidence": "osv:DEBIAN-CVE-2026-63387",
    "products": [
      {
        "name": {
          "value": "libevent",
          "evidence": "/affected/0/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [
          {
            "value": "2.1.12-stable-8+deb12u1",
            "evidence": "/affected/0/ranges"
          }
        ],
        "affected_versions": [
          {
            "value": "2.1.12-stable-8",
            "evidence": "/affected/0/versions"
          }
        ]
      },
      {
        "name": {
          "value": "libevent",
          "evidence": "/affected/1/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [
          {
            "value": "2.1.13-stable-1~deb13u1",
            "evidence": "/affected/1/ranges"
          }
        ],
        "affected_versions": [
          {
            "value": "2.1.12-stable-10",
            "evidence": "/affected/1/versions"
          }
        ]
      },
      {
        "name": {
          "value": "libevent",
          "evidence": "/affected/2/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [
          {
            "value": "2.1.13-stable-1",
            "evidence": "/affected/2/ranges"
          }
        ],
        "affected_versions": [
          {
            "value": "2.1.12-stable-10",
            "evidence": "/affected/2/versions"
          },
          {
            "value": "2.1.13-stable-1~deb13u1",
            "evidence": "/affected/2/versions"
          }
        ]
      }
    ],
    "severity": "high",
    "structured": {
      "id": "DEBIAN-CVE-2026-63387",
      "aliases": [
        "DEBIAN-CVE-2026-63387"
      ],
      "metrics": [
        {
          "type": "CVSS_V3",
          "score": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:H"
        }
      ],
      "affected": [
        {
          "ranges": [
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "0"
                },
                {
                  "fixed": "2.1.12-stable-8+deb12u1"
                }
              ]
            }
          ],
          "package": {
            "name": "libevent",
            "purl": "pkg:deb/debian/libevent?arch=source&distro=bookworm",
            "ecosystem": "Debian:12"
          },
          "versions": [
            "2.1.12-stable-8"
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/debian-osv/debian-cve-osv/DEBIAN-CVE-2026-63387.json"
          },
          "ecosystem_specific": {
            "urgency": "not yet assigned"
          }
        },
        {
          "ranges": [
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "0"
                },
                {
                  "fixed": "2.1.13-stable-1~deb13u1"
                }
              ]
            }
          ],
          "package": {
            "name": "libevent",
            "purl": "pkg:deb/debian/libevent?arch=source&distro=trixie",
            "ecosystem": "Debian:13"
          },
          "versions": [
            "2.1.12-stable-10"
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/debian-osv/debian-cve-osv/DEBIAN-CVE-2026-63387.json"
          },
          "ecosystem_specific": {
            "urgency": "not yet assigned"
          }
        },
        {
          "ranges": [
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "0"
                },
                {
                  "fixed": "2.1.13-stable-1"
                }
              ]
            }
          ],
          "package": {
            "name": "libevent",
            "purl": "pkg:deb/debian/libevent?arch=source&distro=forky",
            "ecosystem": "Debian:14"
          },
          "versions": [
            "2.1.12-stable-10",
            "2.1.13-stable-1~deb13u1"
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/debian-osv/debian-cve-osv/DEBIAN-CVE-2026-63387.json"
          },
          "ecosystem_specific": {
            "urgency": "not yet assigned"
          }
        }
      ],
      "modified": "2026-10-27T09:47:33.913118410Z",
      "provider": "osv",
      "upstream": [
        "CVE-2026-63387"
      ],
      "references": [
        "https://security-tracker.debian.org/tracker/CVE-2026-63387"
      ]
    },
    "related_cves": [
      {
        "value": "CVE-2026-63387",
        "evidence": "/upstream"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 460880,
  "published_at": "2026-08-20T18:16:36.723+00:00"
}