CVE-2026-16317

{
  "id": "CVE-2026-16317",
  "sourceIdentifier": "ff89ba41-3aa1-4d27-914a-91399e9639e5",
  "published": "2026-07-21T21:16:49.060",
  "lastModified": "2026-10-24T19:10:00.127",
  "vulnStatus": "Awaiting Analysis",
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "Missing validation of the outer content_type byte on TLS 1.3 encrypted records in s2n-tls allows an active man-in-the-middle to silently discard individual application data records without either endpoint detecting the modification. RFC 8446 Section 5.2 requires that the outer content_type of all encrypted TLS 1.3 records must be application_data (0x17). The s2n-tls AEAD implementation hardcodes this value in the additional authenticated data rather than using the actual wire byte, so the outer content_type is not covered by the authentication tag. \n\n\n\nThis enables selective suppression of application data. In HTTP pipelining scenarios, dropping a TLS record containing an HTTP request can cause request/response desynchronization, where subsequent responses are delivered to the wrong requests. In write-heavy workloads, a dropped record containing a write request can result in undetectable data loss when the client interprets a subsequent success response as confirmation of the dropped write.\n\n\n\nAll TLS 1.3 connections are affected. Both TLS clients and servers are affected. TLS 1.2 and QUIC connections are not affected.\n\n\n\nWe recommend you upgrade s2n-tls to version v1.7.6"
    },
    {
      "lang": "es",
      "value": "La falta de validación del byte content_type externo en los registros cifrados de TLS 1.3 en s2n-tls permite a un man-in-the-middle activo descartar silenciosamente registros individuales de datos de aplicación sin que ninguno de los extremos detecte la modificación. La Sección 5.2 del RFC 8446 requiere que el content_type externo de todos los registros cifrados de TLS 1.3 debe ser application_data (0x17). La implementación AEAD de s2n-tls fija este valor en los datos autenticados adicionales en lugar de usar el byte real en la red, por lo que el content_type externo no está cubierto por la etiqueta de autenticación.\n\nEsto permite la supresión selectiva de datos de aplicación. En escenarios de pipelining HTTP, descartar un registro TLS que contiene una solicitud HTTP puede causar una desincronización de solicitud/respuesta, donde las respuestas subsiguientes se entregan a las solicitudes incorrectas. En cargas de trabajo con muchas escrituras, un registro descartado que contiene una solicitud de escritura puede resultar en una pérdida de datos indetectable cuando el cliente interpreta una respuesta de éxito subsiguiente como confirmación de la escritura descartada.\n\nTodas las conexiones TLS 1.3 están afectadas. Tanto los clientes TLS como los servidores están afectados. Las conexiones TLS 1.2 y QUIC no están afectadas.\n\nRecomendamos que actualice s2n-tls a la versión v1.7.6"
    }
  ],
  "affected": [
    {
      "source": "ff89ba41-3aa1-4d27-914a-91399e9639e5",
      "affectedData": [
        {
          "vendor": "AWS",
          "product": "s2n-tls",
          "defaultStatus": "unaffected",
          "versions": [
            {
              "version": "0",
              "lessThanOrEqual": "1.7.5",
              "versionType": "custom",
              "status": "affected"
            }
          ]
        }
      ]
    }
  ],
  "metrics": {
    "cvssMetricV40": [
      {
        "source": "ff89ba41-3aa1-4d27-914a-91399e9639e5",
        "type": "Secondary",
        "cvssData": {
          "version": "4.0",
          "vectorString": "CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:H/VA:L/SC:N/SI:L/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X",
          "baseScore": 8.3,
          "baseSeverity": "HIGH",
          "attackVector": "NETWORK",
          "attackComplexity": "LOW",
          "attackRequirements": "PRESENT",
          "privilegesRequired": "NONE",
          "userInteraction": "NONE",
          "vulnConfidentialityImpact": "NONE",
          "vulnIntegrityImpact": "HIGH",
          "vulnAvailabilityImpact": "LOW",
          "subConfidentialityImpact": "NONE",
          "subIntegrityImpact": "LOW",
          "subAvailabilityImpact": "NONE",
          "exploitMaturity": "NOT_DEFINED",
          "confidentialityRequirement": "NOT_DEFINED",
          "integrityRequirement": "NOT_DEFINED",
          "availabilityRequirement": "NOT_DEFINED",
          "modifiedAttackVector": "NOT_DEFINED",
          "modifiedAttackComplexity": "NOT_DEFINED",
          "modifiedAttackRequirements": "NOT_DEFINED",
          "modifiedPrivilegesRequired": "NOT_DEFINED",
          "modifiedUserInteraction": "NOT_DEFINED",
          "modifiedVulnConfidentialityImpact": "NOT_DEFINED",
          "modifiedVulnIntegrityImpact": "NOT_DEFINED",
          "modifiedVulnAvailabilityImpact": "NOT_DEFINED",
          "modifiedSubConfidentialityImpact": "NOT_DEFINED",
          "modifiedSubIntegrityImpact": "NOT_DEFINED",
          "modifiedSubAvailabilityImpact": "NOT_DEFINED",
          "Safety": "NOT_DEFINED",
          "Automatable": "NOT_DEFINED",
          "Recovery": "NOT_DEFINED",
          "valueDensity": "NOT_DEFINED",
          "vulnerabilityResponseEffort": "NOT_DEFINED",
          "providerUrgency": "NOT_DEFINED"
        }
      }
    ],
    "cvssMetricV31": [
      {
        "source": "ff89ba41-3aa1-4d27-914a-91399e9639e5",
        "type": "Secondary",
        "cvssData": {
          "version": "3.1",
          "vectorString": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:L",
          "baseScore": 6.5,
          "baseSeverity": "MEDIUM",
          "attackVector": "NETWORK",
          "attackComplexity": "HIGH",
          "privilegesRequired": "NONE",
          "userInteraction": "NONE",
          "scope": "UNCHANGED",
          "confidentialityImpact": "NONE",
          "integrityImpact": "HIGH",
          "availabilityImpact": "LOW"
        },
        "exploitabilityScore": 2.2,
        "impactScore": 4.2
      }
    ],
    "ssvcV203": [
      {
        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "ssvcData": {
          "timestamp": "2026-07-22T19:31:33.777230Z",
          "id": "CVE-2026-16317",
          "options": [
            {
              "exploitation": "none"
            },
            {
              "automatable": "no"
            },
            {
              "technicalImpact": "partial"
            }
          ],
          "role": "CISA Coordinator",
          "version": "2.0.3"
        }
      }
    ]
  },
  "weaknesses": [
    {
      "source": "ff89ba41-3aa1-4d27-914a-91399e9639e5",
      "type": "Secondary",
      "description": [
        {
          "lang": "en",
          "value": "CWE-354"
        }
      ]
    }
  ],
  "references": [
    {
      "url": "https://aws.amazon.com/security/security-bulletins/2026-062-aws/",
      "source": "ff89ba41-3aa1-4d27-914a-91399e9639e5"
    },
    {
      "url": "https://github.com/aws/s2n-tls/releases/tag/v1.7.6",
      "source": "ff89ba41-3aa1-4d27-914a-91399e9639e5"
    },
    {
      "url": "https://github.com/aws/s2n-tls/security/advisories/GHSA-684c-v35q-fvx7",
      "source": "ff89ba41-3aa1-4d27-914a-91399e9639e5"
    }
  ]
}