CVE-2026-86688
HighCVSS 7.4Summary
Session Fixation vulnerability in team-alembic ash_authentication allows an attacker who can plant a session identifier in a victim's browser to hold an authenticated session once that victim signs in. AshAuthentication.Plug.Helpers.store_in_session/2 writes the authenticated subject into the existing session with Plug.Conn.put_session/3 and never calls Plug.Conn.configure_session(renew: true), so the identifier the visitor arrived with carries into their authenticated session. Every authentication event reaches this one function: the default success/4 injected by AshAuthentication.Phoenix.Controller.__using__/1, the AuthController emitted by mix ash_authentication_phoenix.install, and remember-me auto-login. AshAuthentication.Phoenix.Plug.store_in_session/2 is a defdelegate to it. Logout does not close the window either, because clear_session/2 ends with Plug.Conn.clear_session/1, which clears session contents but leaves the identifier intact, so a planted identifier survives a logout-then-login cycle. This issue affects ash_authentication: from 0.2.0 before 4.15.0 and from 5.0.0-rc.0 before 5.0.0-rc.14.
Risk Assessment
An attacker can hijack an authenticated user's session, potentially leading to unauthorized access to accounts and data.
Recommendation
It is recommended to upgrade ash_authentication to version 4.15.0 or 5.0.0-rc.14 and implement session renewal mechanisms after login.
Other vulnerabilities in ash_authentication
See all- CVE-2026-76949Critical
A vulnerability in the ash_authentication library (Elixir) allows an attacker who can plant a remember-me cookie in a victim's browser to replace the victim's authenticated session with one for the attacker's own account. The issue stems from a mismatch between the session keys used by the guard and the reader, causing remember-me sign-in to run on every request.
- CVE-2026-91039Critical
Vulnerability in ash_authentication related to dynamic_oidc strategy that fails to maintain proper identity namespace separation across connections. An attacker controlling one connection can be signed in as a local user created through a different connection because user identities are not correctly separated.
- CVE-2026-88952Critical
In ash_authentication there is an improper authentication vulnerability that allows an attacker to sign in as another user by linking their OAuth2 identity to an account that is not theirs. The attacker can attach a verified email to an account matched on other attributes, leading to session hijacking.
Original NVD description (English source)
Session Fixation vulnerability in team-alembic ash_authentication allows an attacker who can plant a session identifier in a victim's browser to hold an authenticated session once that victim signs in. AshAuthentication.Plug.Helpers.store_in_session/2 writes the authenticated subject into the existing session with Plug.Conn.put_session/3 and never calls Plug.Conn.configure_session(renew: true), so the identifier the visitor arrived with carries into their authenticated session. Every authentication event reaches this one function: the default success/4 injected by AshAuthentication.Phoenix.Controller.__using__/1, the AuthController emitted by mix ash_authentication_phoenix.install, and remember-me auto-login. AshAuthentication.Phoenix.Plug.store_in_session/2 is a defdelegate to it. Logout does not close the window either, because clear_session/2 ends with Plug.Conn.clear_session/1, which clears session contents but leaves the identifier intact, so a planted identifier survives a logout-then-login cycle. This issue affects ash_authentication: from 0.2.0 before 4.15.0 and from 5.0.0-rc.0 before 5.0.0-rc.14.