An authenticated attacker with write access to the AuthenticationFilter custom resource can supply an arbitrary spec.basic.realm or spec.jwt.realm string. The Gateway Fabric engine inserts that value directly into the shared nginx.conf as an auth_basic directive, without escaping or validation. Because the string is not protected, the attacker can close the opening quote and the surrounding location block and inject any Nginx directive. This flaw allows alteration of the gateway’s data‑plane configuration, enabling the reader of co‑located tenants’ secrets, SSRF through proxy_pass, reading the pod ServiceAccount token, or hijacking other tenants’ routes. It is a control‑plane vulnerability; the data plane itself is not exposed.

F5 NGINX Gateway Fabric. All releases that include the AuthenticationFilter CRD are affected. No specific version numbers are listed, so any current, supported deployment using the AuthenticationFilter is at risk and the CVE does not cover end‑of‑support versions.

The CVSS score of 8.7 denotes high severity. The EPSS score of less than 1% indicates a very low exploitation probability. The attack requires an authenticated user with write privileges on AuthenticationFilter and secrets, which limits the attack surface to privileged roles. The attacker can inject arbitrary Nginx directives, potentially reading other tenants’ secrets, hijacking routes, or causing SSRF attacks. The vulnerability is not listed in the CISA KEV catalog.