CVE-2026-71554

{
  "id": "CVE-2026-71554",
  "sourceIdentifier": "[email protected]",
  "published": "2026-08-06T22:18:32.403",
  "lastModified": "2026-10-24T15:10:00.190",
  "vulnStatus": "Deferred",
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "h2 is a pure-Python implementation of a HTTP/2 protocol stack. Versions up to and including 4.4.0 accept request header blocks containing more than one Host header, and forward every Host header to the consuming application. Where the consumer downgrades HTTP/2 to HTTP/1.1, the resulting request carries two Host header lines, providing a request smuggling primitive. This issue is fixed in version 4.4.1."
    },
    {
      "lang": "es",
      "value": "h2 es una implementación puramente en Python de una pila del protocolo HTTP/2. Las versiones hasta la 4.4.0 inclusive aceptan bloques de encabezado de solicitud que contienen más de un encabezado Host, y reenvían cada encabezado Host a la aplicación consumidora. Cuando el consumidor degrada HTTP/2 a HTTP/1.1, la solicitud resultante lleva dos líneas de encabezado Host, lo que proporciona una primitiva de contrabando de solicitudes. Este problema se corrige en la versión 4.4.1."
    }
  ],
  "affected": [
    {
      "source": "[email protected]",
      "affectedData": [
        {
          "vendor": "python-hyper",
          "product": "h2",
          "versions": [
            {
              "version": "< 4.4.1",
              "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: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
      }
    ],
    "ssvcV203": [
      {
        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "ssvcData": {
          "timestamp": "2026-08-08T02:49:21.263516Z",
          "id": "CVE-2026-71554",
          "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-444"
        }
      ]
    }
  ],
  "references": [
    {
      "url": "https://github.com/python-hyper/h2/commit/292a40829feefda98c8509dcdbbb4a57af9bd6a6",
      "source": "[email protected]"
    },
    {
      "url": "https://github.com/python-hyper/h2/security/advisories/GHSA-6hr6-w5qg-qmwg",
      "source": "[email protected]"
    }
  ]
}