{"id":"GHSA-q8r6-xj3f-wrrm","summary":"SimpleSAMLphp SP accepts a response from an unexpected IdP when unsigned `Response/InResponseTo` is combined with a signed assertion lacking `SubjectConfirmationData/InResponseTo`","details":"## Summary\n\nSimpleSAMLphp's SAML SP ACS path does not enforce the IdP selected for an SP-initiated login. If a saved SP state contains `ExpectedIssuer = IdP A`, but the ACS receives a valid response from `IdP B`, the code logs a warning and continues processing instead of rejecting the response.\n\nThat behavior becomes security-relevant when combined with the response-processing rule that accepts an unsigned `samlp:Response/@InResponseTo` outside the signed assertion whenever the signed assertion's `SubjectConfirmationData` does not carry its own `InResponseTo`. A response issued by one trusted IdP can therefore be bound to SP state created for another IdP.\n\n## Impact\n\nIn a multi-IdP deployment, a lower-trust IdP can satisfy SP state created for a different expected IdP. This can bypass an SP flow that intentionally routes the user to a specific IdP, including deployments that set `enable_unsolicited` to `false` to prevent IdP-initiated logins.\n\nThe impact is highest when the SP trusts multiple IdPs with different assurance levels, tenant boundaries, or attribute namespaces, and application authorization depends on the selected/expected IdP. In those deployments this is an authentication/authorization bypass candidate. Impact strongly depends on whether an attacker can obtain a signed IdP-initiated assertion from a lower-trust trusted IdP and whether the downstream application maps identifiers globally.","aliases":["CVE-2026-49284"],"modified":"2026-09-10T03:50:52.943966319Z","published":"2026-07-02T20:47:21Z","database_specific":{"github_reviewed_at":"2026-07-02T20:47:21Z","nvd_published_at":null,"cwe_ids":["CWE-345"],"severity":"HIGH","github_reviewed":true},"references":[{"type":"WEB","url":"https://github.com/simplesamlphp/simplesamlphp/security/advisories/GHSA-q8r6-xj3f-wrrm"},{"type":"PACKAGE","url":"https://github.com/simplesamlphp/simplesamlphp"}],"affected":[{"package":{"name":"simplesamlphp/simplesamlphp","ecosystem":"Packagist","purl":"pkg:composer/simplesamlphp/simplesamlphp"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"2.5.0"},{"fixed":"2.5.2"}]}],"versions":["v2.5.0","v2.5.1"],"database_specific":{"last_known_affected_version_range":"\u003c= 2.5.1","source":"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/07/GHSA-q8r6-xj3f-wrrm/GHSA-q8r6-xj3f-wrrm.json"}},{"package":{"name":"simplesamlphp/simplesamlphp","ecosystem":"Packagist","purl":"pkg:composer/simplesamlphp/simplesamlphp"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"2.4.7"}]}],"versions":["1.16.0","1.16.0-rc1","1.16.1","1.16.2","1.16.3","1.19.8","1.19.9","2.0.2","2.0.3","2.0.4","2.0.4-alpha.1","2.0.5","2.1.0","2.1.0-rc1","v1.12.0","v1.13.0","v1.13.0-rc1","v1.13.0-rc2","v1.13.1","v1.13.2","v1.14.0","v1.14.0-rc1","v1.14.1","v1.14.10","v1.14.11","v1.14.12","v1.14.13","v1.14.14","v1.14.15","v1.14.16","v1.14.17","v1.14.2","v1.14.3","v1.14.4","v1.14.5","v1.14.6","v1.14.7","v1.14.8","v1.14.9","v1.15.0","v1.15.0-rc1","v1.15.0-rc2","v1.15.0-rc3","v1.15.1","v1.15.2","v1.15.3","v1.15.4","v1.17.0","v1.17.0-rc1","v1.17.0-rc2","v1.17.0-rc3","v1.17.1","v1.17.2","v1.17.3","v1.17.4","v1.17.5","v1.17.6","v1.17.7","v1.17.8","v1.18.0","v1.18.0-rc1","v1.18.0-rc2","v1.18.1","v1.18.2","v1.18.3","v1.18.4","v1.18.5","v1.18.6","v1.18.7","v1.18.8","v1.19.0","v1.19.0-rc1","v1.19.1","v1.19.2","v1.19.3","v1.19.4","v1.19.5","v1.19.6","v1.19.7","v2.0.0","v2.0.0-beta.1","v2.0.0-beta.11","v2.0.0-beta.2","v2.0.0-beta.3","v2.0.0-beta.4","v2.0.0-beta99","v2.0.0-rc1","v2.0.0-rc2","v2.0.0-rc3","v2.0.1","v2.0.10","v2.0.11","v2.0.12","v2.0.13","v2.0.14","v2.0.15","v2.0.6","v2.0.7","v2.0.8","v2.0.9","v2.1.1","v2.1.2","v2.1.3","v2.1.4","v2.1.5","v2.1.6","v2.1.7","v2.1.8","v2.2.0","v2.2.1","v2.2.2","v2.2.3","v2.2.4","v2.2.5","v2.2.6","v2.3.0","v2.3.1","v2.3.10","v2.3.11","v2.3.2","v2.3.3","v2.3.4","v2.3.5","v2.3.6","v2.3.7","v2.3.8","v2.3.9","v2.4.0","v2.4.1","v2.4.2","v2.4.3","v2.4.4","v2.4.5","v2.4.6"],"database_specific":{"last_known_affected_version_range":"\u003c= 2.4.6","source":"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/07/GHSA-q8r6-xj3f-wrrm/GHSA-q8r6-xj3f-wrrm.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:H/A:N"}]}