{"id":"CVE-2026-49284","title":"SimpleSAMLphp SP accepts a response from an unexpected IdP when unsigned `Response/InResponseTo` is combined with a signed assertion lacking `SubjectConfirmationData/InResponseTo`","summary":"SimpleSAMLphp SP accepts a response from an unexpected IdP when unsigned `Response/InResponseTo` is combined with a signed assertion lacking `SubjectConfirmationData/InResponseTo`","severity":"high","cvss":7.1,"cwe":["CWE-345"],"vendor":"simplesamlphp","product":"simplesamlphp/simplesamlphp","ecosystem":"composer","affected":["simplesamlphp/simplesamlphp >= 2.5.0, <= 2.5.1","simplesamlphp/simplesamlphp <= 2.4.6"],"patched":["simplesamlphp/simplesamlphp 2.5.2","simplesamlphp/simplesamlphp 2.4.7"],"published":"2026-07-02","updated":"2026-07-02","source":"GHSA","sourceUrl":"https://github.com/advisories/GHSA-q8r6-xj3f-wrrm","references":[{"url":"https://github.com/simplesamlphp/simplesamlphp/security/advisories/GHSA-q8r6-xj3f-wrrm"},{"url":"https://github.com/advisories/GHSA-q8r6-xj3f-wrrm"}],"tags":["ghsa","composer"],"ingestedAt":"2026-07-02T21:44:45.094Z","epss":0.00222,"epssPercentile":0.13071,"slug":"CVE-2026-49284","body":"## Overview\n\n## 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.\n\n## Affected packages\n\n- `simplesamlphp/simplesamlphp >= 2.5.0, <= 2.5.1`\n- `simplesamlphp/simplesamlphp <= 2.4.6`\n\n## Remediation\n\nUpgrade to a patched release:\n\n- `simplesamlphp/simplesamlphp 2.5.2`\n- `simplesamlphp/simplesamlphp 2.4.7`","depth":"twilight","depthScore":39,"depthScoreParts":{"impact":39.1,"likelihood":0,"exploitation":0,"ransomware":0},"changes":[]}