CVE-2026-17107 in Multicluster Engine for Kubernetes
Summary
by MITRE • 07/24/2026
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.
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Analysis
by VulDB Data Team • 07/24/2026
This vulnerability exists within the cluster-proxy service-proxy component of Red Hat Advanced Cluster Management for Kubernetes and multicluster-engine environments, representing a critical authorization flaw that enables privilege escalation across managed clusters. The technical implementation fails to properly sanitize impersonation group headers by removing existing caller-supplied values before appending new ones, creating a dangerous condition where malicious actors can inject arbitrary group memberships into proxied requests. The flaw specifically leverages the fact that spoke ServiceAccounts possess unrestricted impersonation permissions, allowing them to act as any user or group within the cluster environment.
The operational impact of this vulnerability is severe and far-reaching, as it allows authenticated hub principals to escalate their privileges from standard user access to full cluster-admin rights across all managed clusters in the multicluster deployment. This represents a fundamental breakdown in the principle of least privilege and provides attackers with complete control over cluster resources, potentially enabling data exfiltration, lateral movement, and persistent access. The vulnerability affects the core multicluster management functionality where requests flow from the hub cluster to spoke clusters through the service-proxy component.
This flaw aligns with CWE-285: Improper Authorization and ATT&CK technique T1548.003: Abuse of Cloud Platform Credentials, specifically targeting the impersonation capabilities within Kubernetes cluster management systems. The vulnerability demonstrates a classic case of insecure input handling where user-supplied headers are blindly appended without proper validation or sanitization, creating an injection vector for privilege escalation attacks.
Organizations should immediately implement mitigations including restricting the permissions of spoke ServiceAccounts to limit their impersonation capabilities, implementing strict header validation and sanitization within the service-proxy component, and deploying network segmentation controls to limit access to the cluster-proxy components. Additionally, monitoring and alerting should be configured to detect unusual impersonation header patterns, and regular security audits should verify that impersonation permissions are properly constrained across all managed clusters. The recommended approach involves applying the latest security patches from Red Hat, implementing zero-trust network policies, and conducting comprehensive privilege reviews of all multicluster management components.