CVE-2026-10090
Description
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.
Statement
The ACM Application Subscription model has been deprecated in newer ACM releases. Red Hat recommends migrating to the GitOps Operator / Argo CD model for application management. See KCS https://access.redhat.com/solutions/7146608 for verification steps to determine if your environment uses the Application Subscription model. Migrate to GitOps/Argo CD application model
The vulnerability exists specifically in the ACM Application Subscription controller (multicluster-operators-subscription). Environments that use the GitOps Operator / Argo CD application model and do not use the ACM Application Subscription model are not exposed to this vulnerability. .
Mitigation
Remove the RBAC aggregation (immediate, targeted)
Delete the ClusterRole that aggregates Application Subscription management permissions into the Kubernetes edit role:
oc delete clusterrole open-cluster-management:multicloud-operators-subscription:rbac-aggregate-edit
Verification:
oc auth can-i create subscriptions.apps.open-cluster-management.io --as=<user> -n <namespace>
Expected result after mitigation: no
Important notes:
This ClusterRole is recreated by the multiclusterhub-operator during reconciliation. Customers must re-apply this mitigation after any ACM operator upgrade, operator pod restart, or MultiClusterHub CR modification until a fixed release is installed.
After deletion, users with only the edit or view roles will no longer be able to create or delete Application Subscription, Channel, or related resources. Users who are bound to open-cluster-management:subscription-admin or who have explicit RBAC grants are unaffected.
Existing Application Subscriptions continue to function normally.
Common Vulnerability Scoring System (CVSS) Score Details
Info alert:Important note
CVSS scores for open source components depend on vendor-specific factors (e.g. version or build chain). Therefore, Red Hat's score and impact rating can be different from NVD and other vendors. Red Hat remains the authoritative CVE Naming Authority (CNA) source for its products and services (see Red Hat classifications).
The following CVSS metrics and score provided are preliminary and subject to review.
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 9 | N/A | 9 |
| Attack Vector | Network | N/A | Network |
| Attack Complexity | Low | N/A | Low |
| Privileges Required | High | N/A | High |
| User Interaction | None | N/A | None |
| Scope | Changed | N/A | Changed |
| Confidentiality | High | N/A | High |
| Integrity Impact | High | N/A | High |
| Availability Impact | Low | N/A | Low |
Vector
Red Hat: CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:H/I:H/A:L
cve.org: CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:H/I:H/A:L
Understanding the Weakness (CWE)
Access Control
Technical Impact: Gain Privileges or Assume Identity
A user can access restricted functionality and/or sensitive information that may include administrative functionality and user accounts.
Acknowledgements
Red Hat would like to thank Christopher Lusk (North Echo Security Research) for reporting this issue.
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