The cluster‑proxy service‑proxy component of RHACM and MCE appends impersonation group headers to proxied requests without first removing caller‑supplied values. Because the spoke ServiceAccount holds unrestricted impersonation permissions, an authenticated hub principal may inject an Impersonate‑Group header into a request. This allows the attacker to gain cluster‑admin rights on every managed cluster, compromising confidentiality, integrity, and availability of the entire multi‑cluster environment. The flaw is a privilege‑escalation vulnerability (CWE‑441).

The vulnerability affects Red Hat Advanced Cluster Management for Kubernetes (RHACM) and Red Hat Multicluster Engine for Kubernetes (MCE). It is present in MCE releases 2.6, 2.8, 2.9, 2.10, 2.11, and 2.17 running on EL9, which are also incorporated in RHACM versions that bundle these MCE components. The specific RHACM version numbers corresponding to these MCE releases are not directly specified in the CVE data but can be inferred from the RHACM releases that include these MCE component versions. Any installation using one of these specific releases is at risk because the cluster‑proxy service‑proxy component does not sanitize impersonation headers supplied by callers.

The CVSS score of 8.5 indicates high severity, but the EPSS score of less than 1% suggests a very low probability of exploitation in the near term. The vulnerability is not included in the CISA KEV catalog. Exploitation requires the attacker to be an authenticated hub principal and to be able to send an HTTP request that reaches the service‑proxy endpoint; the attacker then inserts a forged Impersonate‑Group header. The impact is global to all managed clusters served by the vulnerable configuration.