CVE-2026-44433

{
  "id": "CVE-2026-44433",
  "sourceIdentifier": "[email protected]",
  "published": "2026-07-16T23:16:16.727",
  "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, an adversarial peer could send a STREAM frame carrying just one byte at the largest offset being permitted to obtain additional flow control credit, which under certain circumstances could lead to a Denial of Service. Assuming the application prepares a receive buffer for storing all data that arrive out-of-order, up to the largest offset being received, this behavior could lead to the application allocating large amount of memory with the peer sending only a handful of packets, resulting in memory exhaustion. In addition to the receive buffer allocation strategy, the severity of this vulnerability depends on how the application controls the stream concurrency. In case of the H2O HTTP server, under its default setting, this bug increases the maximum amount of memory allocated per connection by about 4 times. This issue has been fixed by commit 8b178e6."
    },
    {
      "lang": "es",
      "value": "Quicly es una implementación del protocolo IETF QUIC destinada principalmente para su uso dentro del servidor HTTP H2O. Antes del commit 8b178e6, un par adversario podía enviar un frame STREAM que transportaba solo un byte en el mayor offset permitido para obtener crédito adicional de control de flujo, lo que bajo ciertas circunstancias podría llevar a una denegación de servicio. Asumiendo que la aplicación prepara un búfer de recepción para almacenar todos los datos que llegan fuera de orden, hasta el mayor offset recibido, este comportamiento podría llevar a que la aplicación asigne una gran cantidad de memoria con el par enviando solo un puñado de paquetes, resultando en agotamiento de memoria. Además de la estrategia de asignación del búfer de recepción, la gravedad de esta vulnerabilidad depende de cómo la aplicación controla la concurrencia de streams. En el caso del servidor HTTP H2O, bajo su configuración predeterminada, este error aumenta la cantidad máxima de memoria asignada por conexión en aproximadamente 4 veces. Este problema ha sido solucionado por el commit 8b178e6."
    }
  ],
  "affected": [
    {
      "source": "[email protected]",
      "affectedData": [
        {
          "vendor": "h2o",
          "product": "quicly",
          "versions": [
            {
              "version": "< 8b178e6",
              "status": "affected"
            }
          ]
        }
      ]
    }
  ],
  "metrics": {
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        "source": "[email protected]",
        "type": "Secondary",
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          "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L",
          "baseScore": 5.3,
          "baseSeverity": "MEDIUM",
          "attackVector": "NETWORK",
          "attackComplexity": "LOW",
          "privilegesRequired": "NONE",
          "userInteraction": "NONE",
          "scope": "UNCHANGED",
          "confidentialityImpact": "NONE",
          "integrityImpact": "NONE",
          "availabilityImpact": "LOW"
        },
        "exploitabilityScore": 3.9,
        "impactScore": 1.4
      },
      {
        "source": "[email protected]",
        "type": "Primary",
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          "baseScore": 7.5,
          "baseSeverity": "HIGH",
          "attackVector": "NETWORK",
          "attackComplexity": "LOW",
          "privilegesRequired": "NONE",
          "userInteraction": "NONE",
          "scope": "UNCHANGED",
          "confidentialityImpact": "NONE",
          "integrityImpact": "NONE",
          "availabilityImpact": "HIGH"
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        "impactScore": 3.6
      }
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    "ssvcV203": [
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        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "ssvcData": {
          "timestamp": "2026-07-17T15:26:30.321361Z",
          "id": "CVE-2026-44433",
          "options": [
            {
              "exploitation": "none"
            },
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          "role": "CISA Coordinator",
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  "weaknesses": [
    {
      "source": "[email protected]",
      "type": "Secondary",
      "description": [
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          "value": "CWE-400"
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        {
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          "value": "CWE-770"
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  "references": [
    {
      "url": "https://github.com/h2o/quicly/commit/8b178e692c51a3b1031612ef89f03a53aac63c15",
      "source": "[email protected]",
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      "source": "[email protected]",
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}