Security Advisory: Open Redirect in Directus SAML Authentication
Summary
An open redirect vulnerability exists in the Directus SAML authentication callback endpoint. The RelayState parameter is used in redirects without proper validation against an allowlist of permitted domains.
Vulnerability Description
During SAML authentication, the RelayState parameter is intended to preserve the user's original destination. However, while the login initiation flow validates redirect targets against allowed domains, this validation is not applied to the callback endpoint. This allows an attacker to craft a malicious authentication request that redirects users to an arbitrary external URL upon completion.
The vulnerability is present in both the success and error handling paths of the callback.
Impact
Phishing: Users can be redirected to attacker-controlled sites that mimic legitimate login pages
Credential theft: Chained attacks may leverage the redirect to capture OAuth tokens or authorization codes
Trust erosion: Users may lose confidence in the application's security posture
This vulnerability can be exploited without authentication.