Executive brief
OAuth2 Proxy is a tool used to manage user logins for web applications. A bug in certain versions prevents the software from properly clearing a user's session cookie when they are sent to the sign-in page. On shared computers, this could allow a new user to access the previous person's account because the session was never actually terminated.
Technical details
A regression in OAuth2 Proxy (v7.11.0 to v7.15.1) prevents the sign-in page handler from clearing existing session cookies. In environments where the sign-in page is used as a component of the logout flow, the browser may retain a valid session cookie even after the user believes they have logged out. This is classified as insufficient session expiration (CWE-613) and session fixation (CWE-384). An attacker with physical access to a shared workstation can resume the previous user's authenticated session. The issue is resolved in version 7.15.2 by ensuring the session cookie is cleared at the beginning of the sign-in page handler.
Affected products
- OAuth2 Proxy Project OAuth2 Proxy >= 7.11.0, < 7.15.2
Timeline
- 2026-04-14: disclosed
- 2026-04-14: patched: Fixed in version 7.15.2
- 2026-04-14: advisory