CVE-2026-76949
CriticalCVSS 9.1Summary
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.
Risk Assessment
An attacker can hijack the victim's session and capture data entered after login, leading to confidentiality and integrity breaches.
Recommendation
Update ash_authentication to version 4.15.0 or 5.0.0-rc.14 (or later) and review the require_token_presence_for_authentication? configuration.
Other vulnerabilities in ash_authentication
See all- CVE-2026-86688High
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.
- 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)
Authentication Bypass by Spoofing vulnerability in team-alembic ash_authentication allows an attacker who can plant a remember-me cookie in a victim's browser to replace that victim's authenticated session with one for the attacker's own account. AshAuthentication.Plug.Helpers.sign_in_using_remember_me/3 skips re-authenticating an already-signed-in visitor by checking the session for "<subject_name>_token", but store_in_session/2 writes that key only when require_token_presence_for_authentication? is enabled and otherwise writes the bare subject name. At the default setting the guard therefore reads a key that is never written, its already-signed-in branch is unreachable, and the remember-me sign-in runs on every request through the per-request browser pipeline plug. A planted remember-me cookie is consequently honoured even for a visitor holding a live authenticated session, so whatever the victim enters afterwards lands in data the attacker controls. The read path in authenticate_resource_from_session/4 selects the key correctly, so the guard and the reader disagree about which key holds the session. This issue affects ash_authentication: from 4.10.0 before 4.15.0 and from 5.0.0-rc.0 before 5.0.0-rc.14.