CVE-2026-86533: Team-Alembic Ash Authentication

Critical severity, CVSS 9.1. EPSS: 0.9% chance of exploitation in the next 30 days.

Insufficient Session Expiration vulnerability in team-alembic AshAuthentication and AshAuthentication Phoenix allows a revoked session to remain fully authenticated. A resource configured with session_identifier :jti and require_token_presence_for_authentication? disabled stores its session value as <jti>:<subject>. The jti is there so that signing out can revoke that one session. Neither reader consults it: AshAuthentication.Plug.Helpers.authenticate_resource_from_session/4 and AshAuthentication.Phoenix.LiveSession.on_mount/4 both split the value with split_identifier/2, discard the jti and pass the bare subject to AshAuthentication.subject_to_user/3, which reloads the record. The token-presence branch of each function does check its token, calling AshAuthentication.TokenResource.Actions.get_token/3 with the jti and the purpose user. Because the revocation record is never read, neither its revoked state nor its expiry constrains the session, so a session captured before sign-out keeps working. This issue affects ash_authentication: from 4.9.1 before 4.15.0 and from 5.0.0-rc.0 before 5.0.0-rc.14; ash_authentication_phoenix: from 2.10.0 before 2.17.4 and from 3.0.0-rc.0 before 3.0.0-rc.11.

Affected products

• Team-Alembic Ash Authentication: from 4.9.1, before 4.15.0 (fixed in 4.15.0); from 5.0.0-rc.0, before 5.0.0-rc.14 (fixed in 5.0.0-rc.14)
• Team-Alembic Ash Authentication Phoenix: from 2.10.0, before 2.17.4 (fixed in 2.17.4); from 3.0.0-rc.0, before 3.0.0-rc.11 (fixed in 3.0.0-rc.11)

Published 2026-09-17. Last modified 2026-09-18.