CVE-2026-73266: Clusterclaims-controller: confused deputy: tenant-controlled clusterclaim labels propagated to managedcluster, enabling cross-tenant managedclusterset join

Severity: high (CVSS 7.1 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.4% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-08-13 · updated 2026-09-29
Weakness: CWE-441

Description

A flaw was found in the clusterclaims-controller component of Multicluster Engine (MCE). An authenticated tenant can exploit this vulnerability by manipulating ClusterClaim labels. This allows the tenant to force a cluster to join a ManagedClusterSet belonging to another tenant. Such unauthorized access could enable the injection of policies and workloads into other tenants' clusters.

Affected products

Red Hat multicluster engine for Kubernetes 2.10: all versions — fixed in 1787196014
Red Hat multicluster engine for Kubernetes 2.11: all versions — fixed in 1787239442
Red Hat multicluster engine for Kubernetes 2.17: all versions — fixed in 1786577950
Red Hat multicluster engine for Kubernetes 2.6: all versions — fixed in 1787259112
Red Hat multicluster engine for Kubernetes 2.8: all versions — fixed in 1787259059
Red Hat multicluster engine for Kubernetes 2.9: all versions — fixed in 1787195995

How to fix

Upgrade to a fixed version: Red Hat multicluster engine for Kubernetes 2.10 1787196014; Red Hat multicluster engine for Kubernetes 2.11 1787239442; Red Hat multicluster engine for Kubernetes 2.17 1786577950; Red Hat multicluster engine for Kubernetes 2.6 1787259112; Red Hat multicluster engine for Kubernetes 2.8 1787259059; Red Hat multicluster engine for Kubernetes 2.9 1787195995. Check the vendor advisory for mitigations.

References

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