CVE-2025-27773 SimpleSAMLphp SAML2 library has incorrect signature verification for HTTP-Redirect binding
Attackers can bypass SAML signature verification in HTTP-Redirect binding, allowing acceptance of unsigned messages and potential authentication bypass.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2025-27773?
CVE-2025-27773 is a high-severity authentication bypass vulnerability in simplesamlphp saml2, published on 11 Mar 2025. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official 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.
Weakness: CWE-347
Which versions are affected by CVE-2025-27773?
6 open source packages ship an affected version, including simplesamlphp/saml2 and simplesamlphp/saml2-legacy.
| Package | Affected | Fixed in |
|---|---|---|
simplesamlphp/saml2 Packagist | All versions | 4.17.0 |
simplesamlphp/saml2 Packagist | All versions | 4.17.0 |
simplesamlphp/saml2 Packagist | From 5.0.0-alpha.1 | 5.0.0-alpha.20 |
simplesamlphp/saml2 Packagist | From 5.0.0-alpha.1 | 5.0.0-alpha.20 |
simplesamlphp/saml2-legacy Packagist | All versions | 4.17.0 |
simplesamlphp/saml2-legacy Packagist | All versions | 4.17.0 |
How do I fix CVE-2025-27773?
Upgrade simplesamlphp/saml2 to a fixed version for your release line: 4.17.0 or 5.0.0-alpha.20.
Upgrade, and rotate credentials and sessions that may have been exposed. More about Authentication bypass.
Is CVE-2025-27773 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2025-27773 exists.
Sources
Also known as DEBIAN-CVE-2025-27773, DLA-4161-1, GHSA-46r4-f8gj-xg56, UBUNTU-CVE-2025-27773.