Apache Airflow AWS Auth Manager - Host Header Injection Leading to SAML Authentication Bypass

Vulnerability

Overview

In the AWS Auth Manager component of Apache Airflow, the origin of SAML authentication responses is taken from the client-provided value and not validated against the actual instance URL. This means an attacker can present a SAML response originally issued for a different Airflow instance, and the system will accept it [1][2][3].

Exploitation

Method

An attacker who obtains a valid SAML response from one Airflow instance (for example, through passive interception or by being a legitimate user of that other instance) can reuse that response against a separate Airflow instance that uses the same AWS Auth Manager. Because the origin check is missing, the second instance will accept the external SAML assertion as if it were issued for itself [2][3]. No additional authentication on the target instance is required beyond presenting the reused SAML response.

Impact

Successful exploitation allows the attacker to gain authenticated access to a different Airflow instance with whatever privileges are associated with the original SAML assertion. Since different instances can have different access controls and user roles, this bypass may grant unauthorized access to workflows, DAGs, credentials, or data on the target instance [2][3]. The vulnerability is classified as medium severity.

Mitigation

The issue is fixed in version 9.22.0 of the apache-airflow-providers-amazon package. Users of the AWS Auth Manager are strongly advised to upgrade immediately [1][2][3]. The fix was introduced via pull request #61368 and validates the SAML origin against the expected instance URL [4].