A flaw was found in the Application Subscription controller (multicluster-operators-subscription) of Red Hat Advanced Cluster Management for Kubernetes (ACM). A…

A critical privilege escalation vulnerability exists in the Application Subscription controller (multicluster-operators-subscription) of Red Hat Advanced Cluster Management for Kubernetes (ACM). A user with only namespace-scoped 'edit' privileges can create a malicious Channel resource pointing to an attacker-controlled Helm repository and a Subscription resource referencing it. The app-subscription controller applies Helm chart contents using its own elevated authority without verifying the creator's subscription-admin role or restricting resources to the subscription namespace. An attacker can embed cluster-scoped resources such as ClusterRoleBindings in the Helm chart to grant their ServiceAccount the cluster-admin ClusterRole. Successful exploitation results in full cluster-admin privilege escalation across the ACM hub cluster. This behavior contradicts ACM documentation, which states non-subscription-admin users should only have resources deployed into their subscription namespace.