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certfr-2025-avi-0836 — De multiples vulnérabilités ont été découvertes dans Tenable Security Center. Elles permettent à un attaquant de provoq…

certfr-2025-avi-0836

EUVD-2026-238779

fkie_cve-2025-27773

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.

GHSA-46r4-f8gj-xg56 — The SimpleSAMLphp SAML2 library incorrectly verifies signatures for HTTP-Redirect binding

Affected: Packagist: simplesamlphp/saml2, Packagist: simplesamlphp/saml2-legacy

### Summary 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. ### Details

#### What is verified The data['SignedQuery'] is the string that will be verified by the public key.

It is defined here: https://github.com/simplesamlphp/saml2/blob/9545abd0d9d48388f2fa00469c5c1e0294f0303e/src/SAML2/HTTPRedirect.php#L178-L217

THe code will iterate through each parameter name. Notably, sigQuery is overridden each time when processing, making the last of SAMLRequest/SAMLResponse used for sigQuery.

For example, given:

SAMLRequest=a&SAMLResponse=idpsigned

SAMLResponse=idpsigned will be set as sigQuery, then later verified

#### What is actually processed

Processing uses SAMLRequest parameter value first, (if it exists) then SAMLResponse:

https://github.com/simplesamlphp/saml2/blob/9545abd0d9d48388f2fa00469c5c1e0294f0303e/src/SAML2/HTTPRedirect.php#L104-L113

Given this, the contents that are processed might not be the same as the data that is actually verified.

### Exploiting Suppose an attacker has a signed HTTP Redirect binding from IdP, say a signed logout response. :

SAMLResponse=idpsigned&RelayState=...&SigAlg=...&Signature

Then an attacker can append SAMLReq…

UBUNTU-CVE-2025-27773

Affected: Ubuntu:Pro:16.04:LTS: simplesamlphp, Ubuntu:Pro:18.04:LTS: simplesamlphp, Ubuntu:Pro:20.04:LTS: simplesamlphp, Ubuntu:Pro:22.04:LTS: simplesamlphp, Ubuntu:24.04:LTS: simplesamlphp, Ubuntu:25.10: simplesamlphp