CVE-2026-16317

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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", "supportingMedia": [{"type": "text/html", "base64": false, "value": "<p>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. </p><p>This 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.</p><p>All TLS 1.3 connections are affected. Both TLS clients and servers are affected. TLS 1.2 and QUIC connections are not affected.</p><p>We recommend you upgrade s2n-tls to version v1.7.6</p>"}]}], "references": [{"url": "https://github.com/aws/s2n-tls/releases/tag/v1.7.6", "tags": ["release-notes", "patch"]}, {"url": "https://aws.amazon.com/security/security-bulletins/2026-062-aws/", "tags": ["vendor-advisory"]}, {"url": "https://github.com/aws/s2n-tls/security/advisories/GHSA-684c-v35q-fvx7", "tags": ["release-notes"]}], "metrics": [{"format": "CVSS", "scenarios": [{"lang": "en", "value": "GENERAL"}], "cvssV3_1": {"version": "3.1", "attackVector": "NETWORK", "attackComplexity": "HIGH", "privilegesRequired": "NONE", "userInteraction": "NONE", "scope": "UNCHANGED", "confidentialityImpact": "NONE", "integrityImpact": "HIGH", "availabilityImpact": "LOW", "baseSeverity": "MEDIUM", "baseScore": 6.5, "vectorString": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:L"}}, {"format": "CVSS", "scenarios": [{"lang": "en", "value": "GENERAL"}], "cvssV4_0": {"attackVector": "NETWORK", "attackComplexity": "LOW", "attackRequirements": "PRESENT", "privilegesRequired": "NONE", "userInteraction": "NONE", "vulnConfidentialityImpact": "NONE", "subConfidentialityImpact": "NONE", "vulnIntegrityImpact": "HIGH", "subIntegrityImpact": "LOW", "vulnAvailabilityImpact": "LOW", "subAvailabilityImpact": "NONE", "exploitMaturity": "NOT_DEFINED", "Safety": "NOT_DEFINED", "Automatable": "NOT_DEFINED", "Recovery": "NOT_DEFINED", "valueDensity": "NOT_DEFINED", "vulnerabilityResponseEffort": "NOT_DEFINED", "providerUrgency": "NOT_DEFINED", "version": "4.0", "baseSeverity": "HIGH", "baseScore": 8.3, "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"}}], "source": {"discovery": "UNKNOWN"}, "x_generator": {"engine": "Vulnogram 1.0.4"}}, "adp": [{"metrics": [{"other": {"type": "ssvc", "content": {"timestamp": "2026-07-22T19:31:33.777230Z", "id": "CVE-2026-16317", "options": [{"Exploitation": "none"}, {"Automatable": "no"}, {"Technical Impact": "partial"}], "role": "CISA Coordinator", "version": "2.0.3"}}}], "title": "CISA ADP Vulnrichment", "providerMetadata": {"orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "shortName": "CISA-ADP", "dateUpdated": "2026-07-22T19:41:19.156Z"}}]}}

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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", "supportingMedia": [{"type": "text/html", "value": "<p>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. </p><p>This 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.</p><p>All TLS 1.3 connections are affected. Both TLS clients and servers are affected. TLS 1.2 and QUIC connections are not affected.</p><p>We recommend you upgrade s2n-tls to version v1.7.6</p>", "base64": false}]}], "problemTypes": [{"descriptions": [{"lang": "en", "type": "CWE", "cweId": "CWE-354", "description": "CWE-354 Improper validation of integrity check value"}]}], "cpeApplicability": [{"nodes": [{"negate": false, "cpeMatch": [{"criteria": "cpe:2.3:a:aws:s2n-tls:*:*:*:*:*:*:*:*", "vulnerable": true, "versionEndIncluding": "1.7.5", "versionStartIncluding": "0"}], "operator": "OR"}], "operator": "OR"}], "providerMetadata": {"orgId": "ff89ba41-3aa1-4d27-914a-91399e9639e5", "shortName": "AMZN", "dateUpdated": "2026-07-21T20:16:25.683Z"}}}, "cveMetadata": {"cveId": "CVE-2026-16317", "state": "PUBLISHED", "dateUpdated": "2026-07-22T19:41:19.156Z", "dateReserved": "2026-07-20T16:40:27.027Z", "assignerOrgId": "ff89ba41-3aa1-4d27-914a-91399e9639e5", "datePublished": "2026-07-21T20:12:48.047Z", "assignerShortName": "AMZN"}, "dataVersion": "5.2"}

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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 validaci\u00f3n 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 aplicaci\u00f3n sin que ninguno de los extremos detecte la modificaci\u00f3n. La Secci\u00f3n 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 implementaci\u00f3n 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 est\u00e1 cubierto por la etiqueta de autenticaci\u00f3n.\n\nEsto permite la supresi\u00f3n selectiva de datos de aplicaci\u00f3n. En escenarios de pipelining HTTP, descartar un registro TLS que contiene una solicitud HTTP puede causar una desincronizaci\u00f3n 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 p\u00e9rdida de datos indetectable cuando el cliente interpreta una respuesta de \u00e9xito subsiguiente como confirmaci\u00f3n de la escritura descartada.\n\nTodas las conexiones TLS 1.3 est\u00e1n afectadas. Tanto los clientes TLS como los servidores est\u00e1n afectados. Las conexiones TLS 1.2 y QUIC no est\u00e1n afectadas.\n\nRecomendamos que actualice s2n-tls a la versi\u00f3n v1.7.6"}], "id": "CVE-2026-16317", "lastModified": "2026-10-24T19:10:00.127", "metrics": {"cvssMetricV31": [{"cvssData": {"attackComplexity": "HIGH", "attackVector": "NETWORK", "availabilityImpact": "LOW", "baseScore": 6.5, "baseSeverity": "MEDIUM", "confidentialityImpact": "NONE", "integrityImpact": "HIGH", "privilegesRequired": "NONE", "scope": "UNCHANGED", "userInteraction": "NONE", "vectorString": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:L", "version": "3.1"}, "exploitabilityScore": 2.2, "impactScore": 4.2, "source": "ff89ba41-3aa1-4d27-914a-91399e9639e5", "type": "Secondary"}], "cvssMetricV40": [{"cvssData": {"Automatable": "NOT_DEFINED", "Recovery": "NOT_DEFINED", "Safety": "NOT_DEFINED", "attackComplexity": "LOW", "attackRequirements": "PRESENT", "attackVector": "NETWORK", "availabilityRequirement": "NOT_DEFINED", "baseScore": 8.3, "baseSeverity": "HIGH", "confidentialityRequirement": "NOT_DEFINED", "exploitMaturity": "NOT_DEFINED", "integrityRequirement": "NOT_DEFINED", "modifiedAttackComplexity": "NOT_DEFINED", "modifiedAttackRequirements": "NOT_DEFINED", "modifiedAttackVector": "NOT_DEFINED", "modifiedPrivilegesRequired": "NOT_DEFINED", "modifiedSubAvailabilityImpact": "NOT_DEFINED", "modifiedSubConfidentialityImpact": "NOT_DEFINED", "modifiedSubIntegrityImpact": "NOT_DEFINED", "modifiedUserInteraction": "NOT_DEFINED", "modifiedVulnAvailabilityImpact": "NOT_DEFINED", "modifiedVulnConfidentialityImpact": "NOT_DEFINED", "modifiedVulnIntegrityImpact": "NOT_DEFINED", "privilegesRequired": "NONE", "providerUrgency": "NOT_DEFINED", "subAvailabilityImpact": "NONE", "subConfidentialityImpact": "NONE", "subIntegrityImpact": "LOW", "userInteraction": "NONE", "valueDensity": "NOT_DEFINED", "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", "version": "4.0", "vulnAvailabilityImpact": "LOW", "vulnConfidentialityImpact": "NONE", "vulnIntegrityImpact": "HIGH", "vulnerabilityResponseEffort": "NOT_DEFINED"}, "source": "ff89ba41-3aa1-4d27-914a-91399e9639e5", "type": "Secondary"}], "ssvcV203": [{"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "ssvcData": {"id": "CVE-2026-16317", "options": [{"exploitation": "none"}, {"automatable": "no"}, {"technicalImpact": "partial"}], "role": "CISA Coordinator", "timestamp": "2026-07-22T19:31:33.777230Z", "version": "2.0.3"}}]}, "published": "2026-07-21T21:16:49.060", "references": [{"source": "ff89ba41-3aa1-4d27-914a-91399e9639e5", "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"}], "sourceIdentifier": "ff89ba41-3aa1-4d27-914a-91399e9639e5", "vulnStatus": "Awaiting Analysis", "weaknesses": [{"description": [{"lang": "en", "value": "CWE-354"}], "source": "ff89ba41-3aa1-4d27-914a-91399e9639e5", "type": "Secondary"}]}

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