CVE-2026-4740

Summary

A flaw was found in Open Cluster Management (OCM), the technology underlying Red Hat Advanced Cluster Management (ACM). Improper validation of Kubernetes client certificate renewal allows a managed cluster administrator to forge a client certificate that can be approved by the OCM controller. This enables cross-cluster privilege escalation and may allow an attacker to gain control over other managed clusters, including the hub cluster.

Affected Software

Weaknesses

• CWE-295: Improper Certificate Validation

Workarounds

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.

ADP Enrichment

CISA ADP Vulnrichment

• SSVC:
• Exploitation: none
  • Automatable: no
  • Technical Impact: total

rhacm: Open Cluster Management (OCM): Cross-cluster privilege escalation via improper Kubernetes client certificate renewal validation

Additional References

• https://access.redhat.com/security/cve/CVE-2026-4740
• https://bugzilla.redhat.com/show_bug.cgi?id=2450590
• https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-4740.json

References

• https://access.redhat.com/security/cve/CVE-2026-4740
• https://blog.arfevrier.fr/open-cluster-management-cross-cluster-escape/
• https://bugzilla.redhat.com/show_bug.cgi?id=2450590

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