What’s Vulnerable › Vulnerabilities

CVE-2025-27773: SimpleSAMLphp SAML2 library has incorrect signature verification for HTTP-Redirect binding

• Severity: high (CVSS 8.6 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.4% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2025-03-11 · updated 2026-06-17
• Weakness: CWE-347

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.

Affected products

• simplesamlphp saml2: before 4.17.0; from 5.0.0-alpha.1, < 5.0.0-alpha.20

References

• 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
• https://github.com/simplesamlphp/saml2/commit/7867d6099dc7f31bed1ea10e5bea159c5623d2a0
• https://github.com/simplesamlphp/saml2/security/advisories/GHSA-46r4-f8gj-xg56
• https://lists.debian.org/debian-lts-announce/2025/05/msg00013.html

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