The vulnerability exists in the Application Subscription controller (multicluster-operators-subscription) of Red Hat ACM. A user with namespace-scoped edit privileges can create a Channel resource pointing to a Helm repository they control and a Subscription resource referencing it. The controller fetches and applies the Helm chart contents with elevated authority, without verifying the creator's subscription-admin role or restricting resource application to the subscription namespace. This enables deployment of cluster-scoped resources such as ClusterRoleBindings that grant the attacker's ServiceAccount cluster-admin privileges, resulting in full cluster-admin privilege escalation. The vulnerability contradicts ACM documentation that non-subscription-admin users should only deploy resources within their subscription namespace.

Successful exploitation allows an attacker with limited namespace-scoped edit privileges to escalate to full cluster-admin privileges by deploying cluster-scoped resources. This compromises confidentiality, integrity, and availability of the Kubernetes cluster managed by Red Hat ACM. The flaw bypasses intended authorization controls and violates documented security expectations, potentially enabling complete control over the cluster.

Patch status is not yet confirmed — check the vendor advisory at https://access.redhat.com/security/cve/CVE-2026-10090 for current remediation guidance. Until a fix is available, restrict namespace-scoped edit privileges to trusted users only and monitor for suspicious creation of Channel and Subscription resources. Follow Red Hat's official guidance and updates regarding this vulnerability.