CVE-2026-10090: Multicluster-operators-subscription: multicluster-operators-subscription: namespace edit user can deploy cluster-scoped clusterrolebinding and become cluster-admin via application subscription
A flaw was found in the Application Subscription controller (multicluster-operators-subscription) of Red Hat Advanced Cluster Management for Kubernetes (ACM). A user with namespace-scoped "edit" privileges in an ACM hub namespace can create a Channel resource pointing to a Helm repository they control and a Subscription resource referencing it. The app-subscription controller fetches and applies the Helm chart contents with its own elevated authority, without verifying whether the subscription creator holds the "open-cluster-management:subscription-admin" role and without restricting applied resources to the subscription namespace. This allows the attacker to include cluster-scoped resources in the Helm chart, such as a ClusterRoleBinding granting the attacker's ServiceAccount the "cluster-admin" ClusterRole. Successful exploitation results in full cluster-admin privilege escalation. This contradicts the ACM documentation which states that non-subscription-admin users should have resources deployed into the subscription namespace only.
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Configuration
Update/adjust the app-subscription controller so it verifies the Subscription creator holds the “open-cluster-management:subscription-admin” role before fetching and applying Helm chart contents.
Red Hat Advanced Cluster Management for Kubernetes (ACM) app-subscription controller / Application Subscription (multicluster-operators-subscription) authorization model Require subscription-admin role check = open-cluster-management:subscription-admin - Configuration
Update/adjust the controller to restrict all resources rendered/applied from a Helm chart to the Subscription’s namespace (prevent cluster-scoped resources like ClusterRoleBinding from being applied).
Red Hat Advanced Cluster Management for Kubernetes (ACM) app-subscription controller Restrict applied resources to subscription namespace = subscription namespace only - Compensating control
Restrict namespace-scoped “edit” privileges in ACM hub namespaces so users cannot create Application Subscription resources (multicluster-operators-subscription) that can lead to cluster-admin privilege escalation.
Event History
Frequently Asked Questions
Who is exposed to this privilege escalation?
ACM hub namespaces where a user has namespace-scoped "edit" privileges are exposed. The user does not need the "open-cluster-management:subscription-admin" role to exploit the flaw.
What does an attacker need to exploit it?
The attacker needs edit access in an ACM hub namespace and control of a Helm repository. They can create a Channel pointing to that repository and a Subscription that causes the controller to apply a malicious chart.
How does the attacker obtain cluster-admin access?
The attacker includes cluster-scoped resources in the Helm chart, such as a ClusterRoleBinding that grants their ServiceAccount the cluster-admin ClusterRole. The Application Subscription controller applies the chart with elevated authority rather than limiting resources to the subscription namespace.
What configuration assumption is unsafe?
It is unsafe to rely on the documented expectation that users without subscription-admin privileges can deploy only into their subscription namespace. The described controller behavior does not enforce that namespace restriction or verify the subscription-admin role.