Executive brief
Apache Airflow's FAB authentication provider accepts OAuth tokens from Authentik identity providers without validating the token's intended audience. An attacker with a valid token issued by Authentik for any other application can use it to gain unauthorized access to Airflow and impersonate any user named in that token, potentially compromising workflow data and operational control.
Technical details
The Apache Airflow FAB provider's Authentik OAuth integration fails to validate the `issuer` and `audience` claims in received OpenID Connect ID tokens. This is a token validation bypass vulnerability in the OAuth/OIDC implementation. An attacker with a valid token minted by the same Authentik instance for a different client application can present it to Airflow; since the audience claim is never checked, the token is accepted and the attacker is authenticated as the user named in the token. The attack requires network access to Airflow and a valid token from any application served by the target Authentik instance—not necessarily Airflow itself. This issue was previously fixed for Azure AD (CVE-2026-75156) but the Authentik code path was overlooked. Upgrade to apache-airflow-providers-fab version 3.9.0 or later to obtain the fix.
Affected products
- Apache Airflow FAB provider before 3.9.0
Timeline
- 2026-09-16: disclosed
- 2026-09-09: patched: Fix merged to apache/airflow main branch