Description

The SimpleSAMLphp SAML2 library is a PHP library for SAML2 related functionality. Prior to versions 4.17.0 and 5.0.0-alpha.20, there is a signature confusion attack in the HTTPRedirect binding. An attacker with any signed SAMLResponse via the HTTP-Redirect binding can cause the application to accept an unsigned message. Versions 4.17.0 and 5.0.0-alpha.20 contain a fix for the issue.

Classification

CVE ID: CVE-2025-27773

CVSS Base Severity: HIGH

CVSS Base Score: 8.6

CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:H/A:N

Affected Products

Vendor: simplesamlphp

Product: saml2

Exploit Prediction Scoring System (EPSS)

EPSS Score: 0.02% (probability of being exploited)

EPSS Percentile: 3.57% (scored less or equal to compared to others)

EPSS Date: 2025-04-09 (when was this score calculated)

Stakeholder-Specific Vulnerability Categorization (SSVC)

SSVC Exploitation: poc

SSVC Technical Impact: partial

SSVC Automatable: true

References

https://nvd.nist.gov/vuln/detail/CVE-2025-27773
https://github.com/simplesamlphp/saml2/security/advisories/GHSA-46r4-f8gj-xg56
https://github.com/simplesamlphp/saml2/commit/7867d6099dc7f31bed1ea10e5bea159c5623d2a0
https://github.com/simplesamlphp/saml2/blob/9545abd0d9d48388f2fa00469c5c1e0294f0303e/src/SAML2/HTTPRedirect.php#L104-L113
https://github.com/simplesamlphp/saml2/blob/9545abd0d9d48388f2fa00469c5c1e0294f0303e/src/SAML2/HTTPRedirect.php#L178-L217

Timeline