{"dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": {"cveId": "CVE-2026-55953", "assignerOrgId": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db", "state": "PUBLISHED", "assignerShortName": "EEF", "dateReserved": "2026-06-17T17:55:15.686Z", "datePublished": "2026-07-27T15:21:29.327Z", "dateUpdated": "2026-07-27T16:10:57.029Z"}, "containers": {"cna": {"affected": [{"cpes": ["cpe:2.3:a:erlang:erlang\\/otp:*:*:*:*:*:*:*:*"], "defaultStatus": "unaffected", "modules": ["tls_handshake", "ssl_handshake", "ssl"], "packageName": "ssl", "packageURL": "pkg:otp/ssl?repository_url=https:%2F%2Fgithub.com%2Ferlang%2Fotp&vcs_url=git%20https:%2F%2Fgithub.com%2Ferlang%2Fotp.git", "product": "OTP", "programFiles": ["src/tls_handshake.erl", "src/ssl_handshake.erl"], "programRoutines": [{"name": "tls_handshake:hello/5"}, {"name": "ssl_handshake:handle_server_hello_extensions/9"}, {"name": "ssl:connect/2"}, {"name": "ssl:connect/3"}, {"name": "ssl:connect/4"}], "repo": "https://github.com/erlang/otp", "vendor": "Erlang", "versions": [{"changes": [{"at": "11.7.4", "status": "unaffected"}, {"at": "11.6.0.4", "status": "unaffected"}, {"at": "11.2.12.11", "status": "unaffected"}], "lessThan": "*", "status": "affected", "version": "5.3.4", "versionType": "otp"}]}, {"collectionURL": "https://github.com", "cpes": ["cpe:2.3:a:erlang:erlang\\/otp:*:*:*:*:*:*:*:*"], "defaultStatus": "unaffected", "modules": ["tls_handshake", "ssl_handshake", "ssl"], "packageName": "erlang/otp", "packageURL": "pkg:github/erlang/otp", "product": "OTP", "programFiles": ["lib/ssl/src/tls_handshake.erl", "lib/ssl/src/ssl_handshake.erl"], "programRoutines": [{"name": "tls_handshake:hello/5"}, {"name": "ssl_handshake:handle_server_hello_extensions/9"}, {"name": "ssl:connect/2"}, {"name": "ssl:connect/3"}, {"name": "ssl:connect/4"}], "repo": "https://github.com/erlang/otp", "vendor": "Erlang", "versions": [{"changes": [{"at": "29.0.4", "status": "unaffected"}, {"at": "28.5.0.4", "status": "unaffected"}, {"at": "27.3.4.15", "status": "unaffected"}], "lessThan": "*", "status": "affected", "version": "17.0", "versionType": "otp"}, {"changes": [{"at": "064e236414614f9085cbbbd6eacf0e43c02d1b4b", "status": "unaffected"}, {"at": "0a82596d425abe43dc2e0b3d74aa1557ef74051c", "status": "unaffected"}, {"at": "e6ff938116b2872bccc478af7fefb56627285b77", "status": "unaffected"}], "lessThan": "*", "status": "affected", "version": "84adefa331c4159d432d22840663c38f155cd4c1", "versionType": "git"}]}], "configurations": [{"lang": "en", "supportingMedia": [{"base64": false, "type": "text/html", "value": "<p>The vulnerability only affects TLS clients using TLS 1.2 (or earlier) or DTLS. TLS 1.3 client connections perform the cipher suite membership check and are not affected. Servers are not affected. Exploitation additionally requires an on-path (adversary-in-the-middle) attacker between the client and the intended server.</p>"}], "value": "The vulnerability only affects TLS clients using TLS 1.2 (or earlier) or DTLS. TLS 1.3 client connections perform the cipher suite membership check and are not affected. Servers are not affected. Exploitation additionally requires an on-path (adversary-in-the-middle) attacker between the client and the intended server."}], "cpeApplicability": [{"nodes": [{"cpeMatch": [{"criteria": "cpe:2.3:a:erlang:erlang\\/otp:*:*:*:*:*:*:*:*", "versionEndExcluding": "27.3.4.15", "vulnerable": true}, {"criteria": "cpe:2.3:a:erlang:erlang\\/otp:*:*:*:*:*:*:*:*", "versionEndExcluding": "28.5.0.4", "versionStartIncluding": "28.0", "vulnerable": true}, {"criteria": "cpe:2.3:a:erlang:erlang\\/otp:*:*:*:*:*:*:*:*", "versionEndExcluding": "29.0.4", "versionStartIncluding": "29.0", "vulnerable": true}], "negate": false, "operator": "OR"}], "operator": "AND"}], "credits": [{"lang": "en", "type": "finder", "value": "Jonatan M\u00e4nnchen / EEF"}, {"lang": "en", "type": "remediation developer", "value": "Ingela Anderton Andin"}, {"lang": "en", "type": "remediation reviewer", "value": "Jakub Witczak"}], "descriptions": [{"lang": "en", "supportingMedia": [{"base64": false, "type": "text/html", "value": "<p>The Erlang/OTP <tt>ssl</tt> TLS 1.2 (and earlier) and DTLS client does not verify that the cipher suite selected by the server in <tt>ServerHello</tt> was among the suites offered by the client in <tt>ClientHello</tt>. The client-side <tt>tls_handshake:hello/5</tt> handler validates the negotiated protocol version and the downgrade sentinel but hands the server-chosen suite directly to <tt>ssl_handshake:handle_server_hello_extensions/9</tt>, which installs it without a membership check. The TLS 1.3 client path performs this check (per RFC 8446), so it is not affected.</p><p>An on-path attacker between the client and the intended server can respond with a <tt>ServerHello</tt> selecting an anonymous key exchange suite such as <tt>TLS_DH_anon_*</tt> or <tt>TLS_ECDH_anon_*</tt> that the client never offered. Anonymous suites do not require the server to present a certificate, so the entire <tt>verify_peer</tt> and <tt>cacerts</tt> configuration is bypassed: the attacker completes the handshake with its own ephemeral parameters, no certificate is validated, no hostname is checked, and <tt>ssl:connect</tt> returns <tt>{ok, Socket}</tt>. All subsequent application traffic is readable and modifiable by the attacker.</p><p>This issue affects OTP from OTP 17.0 before OTP&nbsp;29.0.4, OTP&nbsp;28.5.0.4 and OTP&nbsp;27.3.4.15, corresponding to ssl from 5.3.4 before 11.7.4, 11.6.0.4 and 11.2.12.11.</p>"}], "value": "The Erlang/OTP ssl TLS 1.2 (and earlier) and DTLS client does not verify that the cipher suite selected by the server in ServerHello was among the suites offered by the client in ClientHello. The client-side tls_handshake:hello/5 handler validates the negotiated protocol version and the downgrade sentinel but hands the server-chosen suite directly to ssl_handshake:handle_server_hello_extensions/9, which installs it without a membership check. The TLS 1.3 client path performs this check (per RFC 8446), so it is not affected.\n\nAn on-path attacker between the client and the intended server can respond with a ServerHello selecting an anonymous key exchange suite such as TLS_DH_anon_* or TLS_ECDH_anon_* that the client never offered. Anonymous suites do not require the server to present a certificate, so the entire verify_peer and cacerts configuration is bypassed: the attacker completes the handshake with its own ephemeral parameters, no certificate is validated, no hostname is checked, and ssl:connect returns {ok, Socket}. All subsequent application traffic is readable and modifiable by the attacker.\n\nThis issue affects OTP from OTP 17.0 before OTP\u00a029.0.4, OTP\u00a028.5.0.4 and OTP\u00a027.3.4.15, corresponding to ssl from 5.3.4 before 11.7.4, 11.6.0.4 and 11.2.12.11."}], "impacts": [{"capecId": "CAPEC-94", "descriptions": [{"lang": "en", "value": "CAPEC-94 Adversary in the Middle (AiTM)"}]}], "metrics": [{"cvssV4_0": {"attackComplexity": "LOW", "attackRequirements": "PRESENT", "attackVector": "NETWORK", "baseScore": 9.1, "baseSeverity": "CRITICAL", "privilegesRequired": "NONE", "subAvailabilityImpact": "NONE", "subConfidentialityImpact": "NONE", "subIntegrityImpact": "NONE", "userInteraction": "NONE", "vectorString": "CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N", "version": "4.0", "vulnAvailabilityImpact": "NONE", "vulnConfidentialityImpact": "HIGH", "vulnIntegrityImpact": "HIGH"}, "format": "CVSS", "scenarios": [{"lang": "en", "value": "GENERAL"}]}], "problemTypes": [{"descriptions": [{"cweId": "CWE-757", "description": "CWE-757 Selection of Less-Secure Algorithm During Negotiation ('Algorithm Downgrade')", "lang": "en", "type": "CWE"}]}], "providerMetadata": {"orgId": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db", "shortName": "EEF", "dateUpdated": "2026-07-27T16:10:57.029Z"}, "references": [{"tags": ["vendor-advisory", "related"], "url": "https://github.com/erlang/otp/security/advisories/GHSA-c6cw-pr89-w882"}, {"tags": ["related"], "url": "https://cna.erlef.org/cves/CVE-2026-55953.html"}, {"tags": ["related"], "url": "https://osv.dev/vulnerability/EEF-CVE-2026-55953"}, {"tags": ["x_version-scheme"], "url": "https://www.erlang.org/doc/system/versions.html#order-of-versions"}, {"tags": ["patch"], "url": "https://github.com/erlang/otp/commit/064e236414614f9085cbbbd6eacf0e43c02d1b4b"}, {"tags": ["patch"], "url": "https://github.com/erlang/otp/commit/0a82596d425abe43dc2e0b3d74aa1557ef74051c"}, {"tags": ["patch"], "url": "https://github.com/erlang/otp/commit/e6ff938116b2872bccc478af7fefb56627285b77"}], "source": {"discovery": "INTERNAL"}, "title": "TLS 1.2 and DTLS client accepts unoffered anonymous cipher suite, bypassing server authentication", "workarounds": [{"lang": "en", "supportingMedia": [{"base64": false, "type": "text/html", "value": "<ul><li>Restrict client connections to TLS 1.3 only by setting <tt>versions</tt> to <tt>['tlsv1.3']</tt> in the client's <tt>ssl</tt> options. The TLS 1.3 client path performs the required cipher suite membership check and is not affected.</li></ul>"}], "value": "* Restrict client connections to TLS 1.3 only by setting versions to ['tlsv1.3'] in the client's ssl options. The TLS 1.3 client path performs the required cipher suite membership check and is not affected."}], "x_generator": {"engine": "cvelib 1.8.0"}}}}

{}

{}

{}

{"affected": [{"configurations": [{"platform": null, "status": "affected", "versions": {"scheme": "generic", "value": "[0,*]"}}], "enrichment": {"confidence": 95.0, "confidence_source": "inferred", "scores": [{"score": 95.0, "source": "inferred"}, {"score": 100.0, "source": "matching"}]}, "product": "erlang/otp", "vendor": "erlang"}, {"configurations": [{"platform": null, "status": "affected", "versions": {"scheme": "semver", "value": "[5.3.4,*]"}}], "enrichment": {"confidence": 100.0, "confidence_source": "matching", "scores": [{"score": 100.0, "source": "matching"}]}, "original": {"product": "OTP", "source": "cna", "vendor": "Erlang"}, "product": "otp", "vendor": "erlang"}, {"configurations": [{"platform": null, "status": "affected", "versions": {"scheme": "semver", "value": "[17.0,*]"}}, {"platform": null, "status": "affected", "versions": {"scheme": "code_commit", "value": "84adefa331c4159d432d22840663c38f155cd4c1"}}], "enrichment": {"confidence": 100.0, "confidence_source": "matching", "scores": [{"score": 100.0, "source": "matching"}]}, "original": {"product": "OTP", "source": "cna", "vendor": "Erlang"}, "product": "otp", "vendor": "erlang"}], "created": "2026-07-27T16:45:03.608761+00:00", "updated": "2026-07-27T16:45:03.608823+00:00", "vendors": ["erlang", "erlang$PRODUCT$erlang/otp", "erlang$PRODUCT$otp"]}