{
  "affected": [
    {
      "ranges": [
        {
          "database_specific": {
            "extracted_events": [
              {
                "introduced": "2.2.0-alpha"
              },
              {
                "fixed": "2.2.2-alpha"
              },
              {
                "introduced": "0"
              },
              {
                "fixed": "2.1.13"
              }
            ],
            "source": [
              "AFFECTED_FIELD",
              "REFERENCES"
            ]
          },
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "df3ecad3a040fd6d4fad4287defe113395de6fd7"
            },
            {
              "fixed": "79ddfb460847999b807cba76d04e73891f29c6ee"
            }
          ],
          "repo": "https://github.com/libevent/libevent",
          "type": "GIT"
        }
      ]
    }
  ],
  "aliases": [
    "GHSA-58rx-7448-jw47"
  ],
  "database_specific": {
    "cna_assigner": "GitHub_M",
    "cwe_ids": [
      "CWE-121",
      "CWE-193",
      "CWE-787"
    ],
    "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/63xxx/CVE-2026-63387.json"
  },
  "details": "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.",
  "id": "CVE-2026-63387",
  "modified": "2026-08-22T03:30:54.204377315Z",
  "published": "2026-08-20T17:53:41.863Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/libevent/libevent/releases/tag/release-2.1.13-stable"
    },
    {
      "type": "WEB",
      "url": "https://github.com/libevent/libevent/releases/tag/release-2.2.2-alpha"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/63xxx/CVE-2026-63387.json"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/libevent/libevent/security/advisories/GHSA-58rx-7448-jw47"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-63387"
    }
  ],
  "schema_version": "1.9.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:H",
      "type": "CVSS_V3"
    }
  ],
  "summary": "Libevent: Off-by-one stack buffer overflow in dnsname_to_labels via crafted DNS server response"
}