A critical (CVSS 9.9) privilege escalation flaw in Red Hat Advanced Cluster Management for Kubernetes lets any user with namespace-scoped edit rights on an ACM hub deploy attacker-controlled cluster-scoped resources and seize cluster-admin.
What Is It
The flaw sits in the Application Subscription controller (multicluster-operators-subscription) of Red Hat Advanced Cluster Management for Kubernetes (ACM). A user holding namespace-scoped "edit" privileges in an ACM hub namespace can create a Channel resource pointing to a Helm repository they control, plus a Subscription resource referencing it. The controller then fetches and applies that Helm chart's contents using its own elevated authority; without checking whether the subscription creator holds the open-cluster-management:subscription-admin role, and without restricting the applied resources to the subscription namespace.
Because cluster-scoped objects are not filtered out, the attacker can ship a ClusterRoleBinding in the chart that grants their own ServiceAccount the cluster-admin ClusterRole. Red Hat classifies the weakness as CWE-267 (Privilege Defined With Unsafe Actions).
Why It Matters
Successful exploitation results in full cluster-admin privilege escalation; total control of the managed Kubernetes environment. The CVSS 3.1 vector is AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H: network-reachable, low complexity, no user interaction, and only low privileges required, with a changed scope and high impact to confidentiality, integrity, and availability. Base score 9.9, rated CRITICAL.
The behavior also directly contradicts ACM documentation, which states that non-subscription-admin users should have resources deployed into the subscription namespace only; meaning operators relying on that documented boundary for tenant isolation do not actually have it.
What's Vulnerable
- Vendor: Red Hat
- Product: Red Hat Advanced Cluster Management for Kubernetes 2 (
cpe:/a:redhat:acm:2) - Package:
rhacm2/multicluster-operators-subscription-rhel9 - Default status: affected
Patch Status
The NVD record was published 2026-08-05 and remains in Received status; no fixed version, remediation guidance, or required-action deadline is present in the supplied data. There is no CISA KEV entry for this CVE, so active exploitation is not currently confirmed. Consult the Red Hat security advisory below for fix availability.
Sources
- Red Hat Security; CVE-2026-10090: https://access.redhat.com/security/cve/CVE-2026-10090
- Red Hat Bugzilla #2483292: https://bugzilla.redhat.com/show_bug.cgi?id=2483292
- NVD, CVE-2026-10090 (published 2026-08-05, source
[email protected])