In the AWS Auth Manager, the SAML authentication process trusts the origin supplied by the client without validating it against the actual instance URL. This flaw allows an attacker to craft a Host header that points to a different Airflow instance and reuse a SAML response generated for that instance to gain access. The result is an authentication bypass that can expose data or controls belonging to separate Airflow deployments. The underlying weakness is a host header injection, identified as CWE‑346.

The vulnerability affects the Apache Airflow Providers Amazon package, used in Apache Airflow deployments that enable the AWS Auth Manager. The specific versions impacted are those preceding the release that introduced the fix; upgrading to version 9.22.0 or later removes the issue.

The CVSS score for this flaw is 5.4, indicating moderate severity, and the EPSS score is below 1%, showing a low probability of exploitation at present. The issue is not listed in the CISA KEV catalog. Exploitation requires an attacker to send requests with a manipulated Host header and provide a valid SAML response from another instance. Once the request is accepted, the authentication bypass occurs, potentially granting the attacker unauthorized access to protected resources.