CVE-2026-44436

{
  "id": "CVE-2026-44436",
  "sourceIdentifier": "[email protected]",
  "published": "2026-07-16T23:16:17.143",
  "lastModified": "2026-10-24T20:10:00.137",
  "vulnStatus": "Analyzed",
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "Quicly is an IETF QUIC protocol implementation intended primarily for use within the H2O HTTP server. Prior to commit 8b178e6, Quicly is vulnerable to a Denial of Service attack through connection state corruption. In QUIC Invariants, the maximum length of a Connection ID is 255 bytes, while QUIC version 1 further restricts the maximum to 20 bytes. Quicly implements QUIC version 1 and therefore its CID buffers are limited to 20 bytes. However, to be able to respond to unknown versions of QUIC, its packet decoder accepts Connection IDs of up to 255 bytes. As its CID buffers are merely 20 bytes long, Quicly must reject QUIC version 1 packets with Connection IDs longer than that. The command line tool bundled with Quicly has had that check, however the library itself lacked such enforcement. As a consequence, when used by applications that lack their own enforcement, the connection state becoming inconsistent to buffer overrun. Fortunately, the overflow stops within the allocated chunk of memory, but nevertheless, the bug leads to assertion failures. This issue has been fixed by commit 8b178e6."
    },
    {
      "lang": "es",
      "value": "Quicly es una implementación del protocolo QUIC de la IETF destinada principalmente para su uso dentro del servidor HTTP H2O. Antes del commit 8b178e6, Quicly es vulnerable a un ataque de denegación de servicio a través de la corrupción del estado de la conexión. En QUIC Invariants, la longitud máxima de un ID de Conexión es de 255 bytes, mientras que la versión 1 de QUIC restringe aún más el máximo a 20 bytes. Quicly implementa la versión 1 de QUIC y, por lo tanto, sus búferes CID están limitados a 20 bytes. Sin embargo, para poder responder a versiones desconocidas de QUIC, su decodificador de paquetes acepta IDs de Conexión de hasta 255 bytes. Como sus búferes CID tienen solo 20 bytes de longitud, Quicly debe rechazar los paquetes de la versión 1 de QUIC con IDs de Conexión más largos que eso. La herramienta de línea de comandos incluida con Quicly tenía esa verificación, sin embargo, la biblioteca misma carecía de tal aplicación. Como consecuencia, cuando es utilizado por aplicaciones que carecen de su propia aplicación, el estado de la conexión se vuelve inconsistente debido a un desbordamiento de búfer. Afortunadamente, el desbordamiento se detiene dentro del fragmento de memoria asignado, pero, sin embargo, el error conduce a fallos de aserción. Este problema ha sido solucionado por el commit 8b178e6."
    }
  ],
  "affected": [
    {
      "source": "[email protected]",
      "affectedData": [
        {
          "vendor": "h2o",
          "product": "quicly",
          "versions": [
            {
              "version": "< 8b178e6",
              "status": "affected"
            }
          ]
        }
      ]
    }
  ],
  "metrics": {
    "cvssMetricV31": [
      {
        "source": "[email protected]",
        "type": "Secondary",
        "cvssData": {
          "version": "3.1",
          "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
          "baseScore": 7.5,
          "baseSeverity": "HIGH",
          "attackVector": "NETWORK",
          "attackComplexity": "LOW",
          "privilegesRequired": "NONE",
          "userInteraction": "NONE",
          "scope": "UNCHANGED",
          "confidentialityImpact": "NONE",
          "integrityImpact": "NONE",
          "availabilityImpact": "HIGH"
        },
        "exploitabilityScore": 3.9,
        "impactScore": 3.6
      }
    ],
    "ssvcV203": [
      {
        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "ssvcData": {
          "timestamp": "2026-07-17T10:48:23.373806Z",
          "id": "CVE-2026-44436",
          "options": [
            {
              "exploitation": "none"
            },
            {
              "automatable": "yes"
            },
            {
              "technicalImpact": "partial"
            }
          ],
          "role": "CISA Coordinator",
          "version": "2.0.3"
        }
      }
    ]
  },
  "weaknesses": [
    {
      "source": "[email protected]",
      "type": "Secondary",
      "description": [
        {
          "lang": "en",
          "value": "CWE-120"
        },
        {
          "lang": "en",
          "value": "CWE-787"
        }
      ]
    }
  ],
  "configurations": [
    {
      "nodes": [
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          "operator": "OR",
          "negate": false,
          "cpeMatch": [
            {
              "vulnerable": true,
              "criteria": "cpe:2.3:a:h2o:quicly:*:*:*:*:*:*:*:*",
              "versionEndExcluding": "2026-05-29",
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  "references": [
    {
      "url": "https://github.com/h2o/quicly/commit/8b178e692c51a3b1031612ef89f03a53aac63c15",
      "source": "[email protected]",
      "tags": [
        "Patch"
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    },
    {
      "url": "https://github.com/h2o/quicly/security/advisories/GHSA-v55w-59qx-2v78",
      "source": "[email protected]",
      "tags": [
        "Third Party Advisory"
      ]
    }
  ]
}