CVE-2025-27773: The SimpleSAMLphp SAML2 library incorrectly verifies signatures for HTTP-Redirect binding
(updated )
There’s 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.
I believe that it exists for v4 only. I have not yet developed a PoC.
V5 is well designed and instead builds the signed query from the same message that will be consumed.
References
- github.com/advisories/GHSA-46r4-f8gj-xg56
- github.com/simplesamlphp/saml2
- github.com/simplesamlphp/saml2/blob/9545abd0d9d48388f2fa00469c5c1e0294f0303e/src/SAML2/HTTPRedirect.php
- github.com/simplesamlphp/saml2/blob/9545abd0d9d48388f2fa00469c5c1e0294f0303e/src/SAML2/HTTPRedirect.php
- github.com/simplesamlphp/saml2/commit/7867d6099dc7f31bed1ea10e5bea159c5623d2a0
- github.com/simplesamlphp/saml2/security/advisories/GHSA-46r4-f8gj-xg56
- lists.debian.org/debian-lts-announce/2025/05/msg00013.html
- nvd.nist.gov/vuln/detail/CVE-2025-27773
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