CVE-2026-63387

{
  "id": "CVE-2026-63387",
  "sourceIdentifier": "[email protected]",
  "published": "2026-08-20T18:16:36.723",
  "lastModified": "2026-10-26T10:10:00.140",
  "vulnStatus": "Awaiting Analysis",
  "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."
    }
  ],
  "affected": [
    {
      "source": "[email protected]",
      "affectedData": [
        {
          "vendor": "libevent",
          "product": "libevent",
          "versions": [
            {
              "version": ">= 2.2.0-alpha, < 2.2.2-alpha",
              "status": "affected"
            },
            {
              "version": "< 2.1.13",
              "status": "affected"
            }
          ]
        }
      ]
    }
  ],
  "metrics": {
    "cvssMetricV31": [
      {
        "source": "[email protected]",
        "type": "Secondary",
        "cvssData": {
          "version": "3.1",
          "vectorString": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:H",
          "baseScore": 7.0,
          "baseSeverity": "HIGH",
          "attackVector": "NETWORK",
          "attackComplexity": "HIGH",
          "privilegesRequired": "NONE",
          "userInteraction": "NONE",
          "scope": "UNCHANGED",
          "confidentialityImpact": "LOW",
          "integrityImpact": "LOW",
          "availabilityImpact": "HIGH"
        },
        "exploitabilityScore": 2.2,
        "impactScore": 4.7
      }
    ],
    "ssvcV203": [
      {
        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "ssvcData": {
          "timestamp": "2026-08-25T15:11:49.042805Z",
          "id": "CVE-2026-63387",
          "options": [
            {
              "exploitation": "poc"
            },
            {
              "automatable": "no"
            },
            {
              "technicalImpact": "partial"
            }
          ],
          "role": "CISA Coordinator",
          "version": "2.0.3"
        }
      }
    ]
  },
  "weaknesses": [
    {
      "source": "[email protected]",
      "type": "Secondary",
      "description": [
        {
          "lang": "en",
          "value": "CWE-121"
        },
        {
          "lang": "en",
          "value": "CWE-193"
        },
        {
          "lang": "en",
          "value": "CWE-787"
        }
      ]
    }
  ],
  "references": [
    {
      "url": "https://github.com/libevent/libevent/releases/tag/release-2.1.13-stable",
      "source": "[email protected]"
    },
    {
      "url": "https://github.com/libevent/libevent/releases/tag/release-2.2.2-alpha",
      "source": "[email protected]"
    },
    {
      "url": "https://github.com/libevent/libevent/security/advisories/GHSA-58rx-7448-jw47",
      "source": "[email protected]"
    },
    {
      "url": "https://github.com/libevent/libevent/security/advisories/GHSA-58rx-7448-jw47",
      "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0"
    }
  ]
}