cve-2026-63387

{
  "cvss": 7.0,
  "datePublished": "2026-08-20T18:16:36.723",
  "dateUpdated": "2026-10-26T10:10:00.140",
  "description": "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",
  "raw": {
    "affected": [
      {
        "affectedData": [
          {
            "product": "libevent",
            "vendor": "libevent",
            "versions": [
              {
                "status": "affected",
                "version": ">= 2.2.0-alpha, < 2.2.2-alpha"
              },
              {
                "status": "affected",
                "version": "< 2.1.13"
              }
            ]
          }
        ],
        "source": "security-advisories@github.com"
      }
    ],
    "cveTags": [],
    "descriptions": [
      {
        "lang": "en",
        "value": "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."
      },
      {
        "lang": "es",
        "value": "Libevent es una biblioteca de notificación de eventos. Antes de 2.1.13 y 2.2.2-alpha, libevent tiene un desbordamiento de búfer de pila por un byte en evdns.c cuando dnsname_to_labels formatea un registro DNS que contiene un nombre al final del búfer de pila de 64 KB asignado por evdns_server_request_format_response. La verificación de la etiqueta final permite que j más label_len más uno sea igual a buf_len, después de lo cual el byte nulo de terminación se escribe en buf[buf_len]. Una respuesta de servidor DNS manipulada que contiene datos PTR, CNAME, MX, NS o SOA puede desencadenar la escritura fuera de límites de un byte y bloquear o corromper el proceso. Este problema está solucionado en las versiones 2.1.13 y 2.2.2-alpha."
      }
    ],
    "id": "CVE-2026-63387",
    "lastModified": "2026-10-26T10:10:00.140",
    "metrics": {
      "cvssMetricV31": [
        {
          "cvssData": {
            "attackComplexity": "HIGH",
            "attackVector": "NETWORK",
            "availabilityImpact": "HIGH",
            "baseScore": 7.0,
            "baseSeverity": "HIGH",
            "confidentialityImpact": "LOW",
            "integrityImpact": "LOW",
            "privilegesRequired": "NONE",
            "scope": "UNCHANGED",
            "userInteraction": "NONE",
            "vectorString": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:H",
            "version": "3.1"
          },
          "exploitabilityScore": 2.2,
          "impactScore": 4.7,
          "source": "security-advisories@github.com",
          "type": "Secondary"
        }
      ],
      "ssvcV203": [
        {
          "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
          "ssvcData": {
            "id": "CVE-2026-63387",
            "options": [
              {
                "exploitation": "poc"
              },
              {
                "automatable": "no"
              },
              {
                "technicalImpact": "partial"
              }
            ],
            "role": "CISA Coordinator",
            "timestamp": "2026-08-25T15:11:49.042805Z",
            "version": "2.0.3"
          }
        }
      ]
    },
    "published": "2026-08-20T18:16:36.723",
    "references": [
      {
        "source": "security-advisories@github.com",
        "url": "https://github.com/libevent/libevent/releases/tag/release-2.1.13-stable"
      },
      {
        "source": "security-advisories@github.com",
        "url": "https://github.com/libevent/libevent/releases/tag/release-2.2.2-alpha"
      },
      {
        "source": "security-advisories@github.com",
        "url": "https://github.com/libevent/libevent/security/advisories/GHSA-58rx-7448-jw47"
      },
      {
        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "url": "https://github.com/libevent/libevent/security/advisories/GHSA-58rx-7448-jw47"
      }
    ],
    "sourceIdentifier": "security-advisories@github.com",
    "vulnStatus": "Awaiting Analysis",
    "weaknesses": [
      {
        "description": [
          {
            "lang": "en",
            "value": "CWE-121"
          },
          {
            "lang": "en",
            "value": "CWE-193"
          },
          {
            "lang": "en",
            "value": "CWE-787"
          }
        ],
        "source": "security-advisories@github.com",
        "type": "Secondary"
      }
    ]
  },
  "severity": "HIGH",
  "source": "nvd",
  "title": "Libevent is an event notification library"
}