CVE-2025-65954: SimpleSAMLphp-casserver open redirect in logout endpoint

Executive brief

A vulnerability in the SimpleSAMLphp CAS server module allows attackers to redirect users to malicious websites. This occurs during the logout process when the system incorrectly trusts a web address provided in the logout request. Attackers can use this to create convincing phishing links that appear to come from a trusted corporate login portal, potentially leading to credential theft or further social engineering attacks.

Technical details

An open redirect vulnerability (CWE-601) exists in the LogoutController of the SimpleSAMLphp casserver module. The logout endpoint accepts a 'url' query parameter and fails to validate it against a list of trusted service URLs before performing a redirection. This can be exploited by a remote attacker who crafts a malicious link; when a user clicks the link, they are redirected to an arbitrary external site. The impact is highest when 'enable_logout' and 'skip_logout_page' are both set to true in the module configuration. The issue is fixed in versions 6.3.1 and 7.0.0.

Affected products

• SimpleSAMLphp simplesamlphp-module-casserver >= 7.0.0-rc1, < 7.0.0-rc3; < 6.3.1

Timeline

• 2025-05-14: disclosed
• 2026-05-15: advisory: GitHub Advisory published

References

• https://api.github.com/users/pradtke
• https://github.com/pradtke
• https://api.github.com/users/pradtke/gists%7B/gist_id%7D
• https://api.github.com/users/pradtke/repos
• https://avatars.githubusercontent.com/u/932934?v=4
• https://api.github.com/users/pradtke/events%7B/privacy%7D