CVE-2026-17107
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.
Statement
A flaw was found in the cluster-proxy service-proxy component of Red Hat Advanced Cluster Management for Kubernetes and multicluster-engine that allows an authenticated hub principal to escalate privileges to cluster-admin across all managed clusters. This is due to improper handling of impersonation group headers, enabling unauthorized administrative access. While the impact of successful exploitation is severe, the attack requires authenticated access to the ACM hub cluster, which is a management-plane component not typically exposed to untrusted networks. Exploitation also depends on knowledge of the cluster-proxy architecture and deliberate construction of requests targeting specific managed clusters. These prerequisites significantly reduce the likelihood of opportunistic or widespread exploitation.
Mitigation
Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base, or stability.
Common Vulnerability Scoring System (CVSS) Score Details
Info alert:Important note
CVSS scores for open source components depend on vendor-specific factors (e.g. version or build chain). Therefore, Red Hat's score and impact rating can be different from NVD and other vendors. Red Hat remains the authoritative CVE Naming Authority (CNA) source for its products and services (see Red Hat classifications).
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 8.5 | N/A | 8.5 |
| Attack Vector | Network | N/A | Network |
| Attack Complexity | High | N/A | High |
| Privileges Required | Low | N/A | Low |
| User Interaction | None | N/A | None |
| Scope | Changed | N/A | Changed |
| Confidentiality | High | N/A | High |
| Integrity Impact | High | N/A | High |
| Availability Impact | High | N/A | High |
Vector
Red Hat: CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:H/I:H/A:H
cve.org: CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:H/I:H/A:H
Understanding the Weakness (CWE)
Non-Repudiation,Access Control
Technical Impact: Gain Privileges or Assume Identity; Hide Activities; Execute Unauthorized Code or Commands
Acknowledgements
Red Hat would like to thank Arpit Jain (GitHub: arpitjain099) and Kahiro Okina (Craftsman Software, Inc.) for reporting this issue.
Frequently Asked Questions
Not sure what something means? Check out our Security Glossary.
Want to get errata notifications? Sign up here.
