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CVE-2026-59243 – Authentication Bypass (JWT Signature Verification Disabled) – Apache Airflow FAB pr

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Summary

CVE-2026-59243 is a critical authentication bypass in the Apache Airflow FAB (Flask-AppBuilder) authentication manager. In the Azure AD OAuth login path, JWT signature verification was disabled by default, allowing an unauthenticated attacker to present forged or unsigned ID tokens and impersonate arbitrary users, including administrators. It carries a CVSS v3.1 base score of 9.8 (Critical).

Technical details

  • Root cause: When decoding Azure AD OAuth ID tokens, the verify_signature parameter defaulted to False, so token signatures were not validated (CWE-347: Improper Verification of Cryptographic Signature). The Authentik OAuth path correctly defaulted to True, reflecting inconsistent configuration across authentication methods.
  • Trigger conditions: An Airflow deployment using the FAB auth manager configured with Azure AD OAuth login.
  • Attack vector: Network — remote and unauthenticated, requiring no privileges or user interaction.
  • Impact: An attacker can submit a forged or alg:none (unsigned) ID token to bypass authentication and impersonate any user, including administrators, resulting in full compromise of confidentiality, integrity, and availability.

Affected software

  • apache-airflow-providers-fab — all versions before 3.7.3.

Severity

  • CVSS v3.1 Base Score: 9.8 (Critical)
  • Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Mitigation and recommended actions

  • Immediate: Upgrade apache-airflow-providers-fab to version 3.7.3 or later, which defaults verify_signature=True.
  • If no patch can be applied: Restrict network access to the Airflow web interface (for example, place it behind a VPN or trusted-network allowlist) and avoid exposing the Azure AD OAuth login path to untrusted networks until the provider is upgraded.

How IONIX identifies potentially affected assets

IONIX matches the following signals against data already collected when it crawled the asset; identifying the technology sends no request beyond that crawl.

  • Page title: Sign In - Airflow

References

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