{"id":"CVE-2026-49283","state":"PUBLISHED","title":"SimpleSAMLphp HTTP-Artifact TLS validator confusion allows cross-IdP authentication bypass","description":"The SimpleSAMLphp SAML2 library is a PHP library for SAML2 related functionality. Prior to versions 4.19.3, 4.20.2, 5.0.6, and 6.2.1, the HTTPArtifact::receive() flow can treat an unsigned embedded SAML Response as cryptographically valid for the wrong identity provider. SOAPClient::addSSLValidator() attaches a TLS-based validator to the outer SOAP ArtifactResponse, while the embedded Response receives a validator that delegates to the outer message and is later checked against metadata selected from the embedded response issuer rather than necessarily the artifact issuer. SOAPClient::validateSSL() returns normally when the TLS public key does not match the key being validated, and SAML2\\Message::validate() treats a validator call that does not throw as successful. In a multi-IdP federation, a malicious or lower-trust IdP can therefore provide an ArtifactResponse containing an unsigned Response that claims a higher-trust victim IdP as issuer and authenticate as arbitrary users with attacker-chosen assertion attributes, NameID, and session data. This issue is fixed in versions 4.19.3, 4.20.2, 5.0.6, and 6.2.1.","publishedAt":"2026-08-19T14:47:05.519Z","updatedAt":"2026-08-19T18:19:10.978Z","severity":{"score":8.7,"label":"High","version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:H/I:H/A:N","source":"GitHub_M"},"assigner":"GitHub_M","products":["simplesamlphp saml2"],"affected":[{"vendor":"simplesamlphp","product":"saml2","versions":[{"version":"< 4.19.3","status":"affected"},{"version":">= 4.20.0, < 4.20.2","status":"affected"},{"version":">= 5.0.0, < 5.0.6","status":"affected"},{"version":">= 6.0.0, < 6.2.1","status":"affected"}]}],"references":["https://github.com/simplesamlphp/saml2/security/advisories/GHSA-6929-8p9f-26jx","https://github.com/simplesamlphp/saml2/commit/4a71b20d8d845579fd0a54d6449c265b40db459d","https://github.com/simplesamlphp/saml2/commit/a2c1ac588c70d7b7998546cf32675fb113f22a5f","https://github.com/simplesamlphp/saml2/commit/d5c213132ef671c0018a11252322034dbddd735a","https://github.com/simplesamlphp/saml2/commit/e2df7992609964951b2a3e7d6566b7427b2a968f"],"weaknesses":["CWE-295"],"ingestedAt":"2026-10-29T20:12:07.131Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/49xxx/CVE-2026-49283.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-49283","state":"PUBLISHED","datePublished":"2026-08-19T14:47:05.519Z","dateUpdated":"2026-08-19T18:19:10.978Z","assignerShortName":"GitHub_M","assignerOrgId":"a0819718-46f1-4df5-94e2-005712e83aaa","dateReserved":"2026-05-28T20:07:58.861Z"},"containers":{"cna":{"title":"SimpleSAMLphp HTTP-Artifact TLS validator confusion allows cross-IdP authentication bypass","descriptions":[{"lang":"en","value":"The SimpleSAMLphp SAML2 library is a PHP library for SAML2 related functionality. Prior to versions 4.19.3, 4.20.2, 5.0.6, and 6.2.1, the HTTPArtifact::receive() flow can treat an unsigned embedded SAML Response as cryptographically valid for the wrong identity provider. SOAPClient::addSSLValidator() attaches a TLS-based validator to the outer SOAP ArtifactResponse, while the embedded Response receives a validator that delegates to the outer message and is later checked against metadata selected from the embedded response issuer rather than necessarily the artifact issuer. SOAPClient::validateSSL() returns normally when the TLS public key does not match the key being validated, and SAML2\\Message::validate() treats a validator call that does not throw as successful. In a multi-IdP federation, a malicious or lower-trust IdP can therefore provide an ArtifactResponse containing an unsigned Response that claims a higher-trust victim IdP as issuer and authenticate as arbitrary users with attacker-chosen assertion attributes, NameID, and session data. This issue is fixed in versions 4.19.3, 4.20.2, 5.0.6, and 6.2.1."}],"affected":[{"vendor":"simplesamlphp","product":"saml2","versions":[{"version":"< 4.19.3","status":"affected"},{"version":">= 4.20.0, < 4.20.2","status":"affected"},{"version":">= 5.0.0, < 5.0.6","status":"affected"},{"version":">= 6.0.0, < 6.2.1","status":"affected"}]}],"references":[{"url":"https://github.com/simplesamlphp/saml2/security/advisories/GHSA-6929-8p9f-26jx","name":"https://github.com/simplesamlphp/saml2/security/advisories/GHSA-6929-8p9f-26jx","tags":["x_refsource_CONFIRM"]},{"url":"https://github.com/simplesamlphp/saml2/commit/4a71b20d8d845579fd0a54d6449c265b40db459d","name":"https://github.com/simplesamlphp/saml2/commit/4a71b20d8d845579fd0a54d6449c265b40db459d","tags":["x_refsource_MISC"]},{"url":"https://github.com/simplesamlphp/saml2/commit/a2c1ac588c70d7b7998546cf32675fb113f22a5f","name":"https://github.com/simplesamlphp/saml2/commit/a2c1ac588c70d7b7998546cf32675fb113f22a5f","tags":["x_refsource_MISC"]},{"url":"https://github.com/simplesamlphp/saml2/commit/d5c213132ef671c0018a11252322034dbddd735a","name":"https://github.com/simplesamlphp/saml2/commit/d5c213132ef671c0018a11252322034dbddd735a","tags":["x_refsource_MISC"]},{"url":"https://github.com/simplesamlphp/saml2/commit/e2df7992609964951b2a3e7d6566b7427b2a968f","name":"https://github.com/simplesamlphp/saml2/commit/e2df7992609964951b2a3e7d6566b7427b2a968f","tags":["x_refsource_MISC"]}],"metrics":[{"cvssV3_1":{"attackComplexity":"LOW","attackVector":"NETWORK","availabilityImpact":"NONE","baseScore":8.7,"baseSeverity":"HIGH","confidentialityImpact":"HIGH","integrityImpact":"HIGH","privilegesRequired":"HIGH","scope":"CHANGED","userInteraction":"NONE","vectorString":"CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:H/I:H/A:N","version":"3.1"}}],"problemTypes":[{"descriptions":[{"cweId":"CWE-295","lang":"en","description":"CWE-295: Improper Certificate Validation","type":"CWE"}]}],"providerMetadata":{"shortName":"GitHub_M","orgId":"a0819718-46f1-4df5-94e2-005712e83aaa","dateUpdated":"2026-08-19T14:47:05.519Z"},"source":{"advisory":"GHSA-6929-8p9f-26jx","discovery":"UNKNOWN"}},"adp":[{"title":"CISA ADP Vulnrichment","metrics":[{"other":{"type":"ssvc","content":{"timestamp":"2026-08-19T18:16:10.690773Z","id":"CVE-2026-49283","options":[{"Exploitation":"none"},{"Automatable":"no"},{"Technical Impact":"total"}],"role":"CISA Coordinator","version":"2.0.3"}}}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2026-08-19T18:19:10.978Z"}}]}}}