External risk intelligence

Apache Airflow FAB Provider Azure AD Token Validation Flaw

CVE advisorySeverity: CRITICAL (CVSS 9.1)

CVE-2026-75156

The vulnerability affects the Apache Airflow web user interface when configured with OAuth authentication. Airflow instances are commonly deployed as web services, and those utilizing web-based authentication providers are often exposed to the internet or accessible via corporate networks to facilitate remote user access.

Halo Surface Signal: 4 out of 5 — likely to be public-facing.

External exposure likelihood

Horizon Alert

Summary of the vulnerability and why it matters

This advisory addresses a critical vulnerability in Apache Airflow's FAB provider, specifically affecting how it handles Azure AD authentication. The flaw allows an attacker to bypass security by creating a malicious Azure tenant and using its tokens to authenticate into the Airflow user interface with elevated privileges. This issue impacts deployments configured for Azure AD OAuth and requires an upgrade to a patched version of the provider.

Unvalidated Azure AD tokens allow unauthorized Airflow access.
Attackers can gain Airflow UI access without prior authentication.
Confirm relevance and exposure to Azure AD OAuth configurations.

Attack Path

How an attacker could exploit the issue

An attacker can impersonate any user, including administrators, by leveraging a misconfiguration in how Azure Active Directory identity tokens are validated. This allows them to gain access to the Airflow user interface.

Requires Azure tenant registration.
Validation failure of identity tokens.
Unauthorized access and role assignment.

Live Threat

Current exploitation, exposure, and threat context

When the FAB auth manager is configured with Azure AD as an OAuth provider, an attacker can forge an Azure AD `id_token` to authenticate to the Airflow UI with elevated privileges. This is possible because the system does not properly validate the issuer or audience of these tokens, allowing tokens minted in any Azure tenant to be accepted.

User authentication data
Unvalidated tokens accepted
Unauthorized UI access

Operational Fix

Recommended remediation, mitigation, and detection steps

The Apache Airflow platform owners or the security team responsible for the FAB provider integration should lead the response, given the vulnerability's impact on authentication. The first practical step is to identify all Airflow deployments using the FAB auth manager with Azure AD, confirm their exposure, and assess business criticality. This will allow for accurate risk prioritization and planning for remediation, which involves upgrading the `apache-airflow-providers-fab` package.

Ownership: Airflow platform or security teams.
Verify first: Azure AD OAuth configuration and reachability.
Action: Upgrade FAB provider package.

Supplementary metadata

CVSS vector

Validate whether this threat affects your internet-facing exposure.

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Frequently asked questions

What is the Apache Airflow FAB provider?

The FAB provider is a component within the Apache Airflow software ecosystem that manages the framework's authentication and user authorization processes. It acts as the bridge between your Airflow environment and external identity services, such as Azure Active Directory, allowing organizations to manage user access to the Airflow user interface through centralized identity management systems.

What is the vulnerability in CVE-2026-75156?

This flaw is classified as CWE-346, which involves improper validation of untrusted inputs. Specifically, the provider fails to verify the issuer or intended audience of identity tokens during the Azure AD login flow. This oversight means the system cannot distinguish between tokens issued by your organization's trusted Azure tenant and those created by an attacker using a separate, unauthorized Azure account.

How does an attacker trigger this CVE-2026-75156 issue?

An attacker triggers this by presenting a forged identity token to the Airflow interface. Because the system relies on a shared Microsoft endpoint for signing keys without checking which tenant issued the token, it accepts any validly signed token from any Azure tenant. Crucially, this does not require access to your internal network or prior credentials; simply registering an external Azure account is sufficient to pass the faulty verification process.

Is my Airflow deployment affected?

You are potentially at risk if your Airflow instance uses the FAB auth manager configured with Azure AD. According to Halo Surface Signal, instances utilizing web-based authentication providers are frequently exposed to the internet or wide corporate networks to support remote access, making those configurations particularly relevant targets for this bypass if they remain on vulnerable versions of the provider.

Do I need to upgrade if I applied previous fixes?

Yes, you must upgrade again. Even if you previously patched for the earlier related CVE, those versions (specifically 3.7.3 through 3.8.0) are still affected because the previous fix only addressed signature verification without implementing the necessary issuer and audience checks. To resolve this, you must update the `apache-airflow-providers-fab` package to version 3.8.1 or later.

References

Written by Nicholas Merritt

Nicholas Merritt is VP of Security Solutions at Halo Security. With more than 25 years across application security, vulnerability prioritization, and offensive security, he helps teams translate threat data into practical exposure validation and remediation focus. He authors Halo Threat Intelligence CVE advisories using Halo Surface Signal and H/A/L/O context to prioritize internet-facing risk.