CVE-2026-17107: Cluster-proxy: impersonation-header injection grants cluster-admin on every managed cluster

Severity: high (CVSS 8.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.6% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-07-24 · updated 2026-09-29
Weakness: CWE-441

Description

A flaw was found in the cluster-proxy service-proxy component used in Red Hat Advanced Cluster Management for Kubernetes (RHACM) and multicluster-engine (MCE). The service-proxy appends impersonation group headers to proxied requests without first removing caller-supplied values, and the spoke ServiceAccount holds unrestricted impersonation permissions. An authenticated hub principal can inject an Impersonate-Group header to escalate to cluster-admin on every managed cluster.

Affected products

Red Hat multicluster engine for Kubernetes 2.10: all versions — fixed in 1784342329
Red Hat multicluster engine for Kubernetes 2.11: all versions — fixed in 1784925025
Red Hat multicluster engine for Kubernetes 2.17: all versions — fixed in 1784926298
Red Hat multicluster engine for Kubernetes 2.6: all versions — fixed in 1783985960
Red Hat multicluster engine for Kubernetes 2.8: all versions — fixed in 1784342329
Red Hat multicluster engine for Kubernetes 2.9: all versions — fixed in 1783278220

How to fix

Upgrade to a fixed version: Red Hat multicluster engine for Kubernetes 2.10 1784342329; Red Hat multicluster engine for Kubernetes 2.11 1784925025; Red Hat multicluster engine for Kubernetes 2.17 1784926298; Red Hat multicluster engine for Kubernetes 2.6 1783985960; Red Hat multicluster engine for Kubernetes 2.8 1784342329; Red Hat multicluster engine for Kubernetes 2.9 1783278220. Check the vendor advisory for mitigations.

References

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