What is the CVSS score of CVE-2026-66793?

CVE-2026-66793 has a CVSS 3.1 base score of 8.8 (High). CVSS vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H. EPSS exploitation probability: 0.6%.

Which versions of Red Hat ACM are affected by CVE-2026-66793?

A privilege escalation vulnerability in Red Hat Advanced Cluster Management allows authenticated users with limited permissions to deploy malicious container images with cluster-admin privileges…

How to fix or mitigate CVE-2026-66793?

Within 24 hours, inventory all Red Hat Advanced Cluster Management deployments and audit which authenticated users currently possess permissions to annotate ManagedClusterAddOn resources; immediately restrict these permissions to administrative accounts only. Within 7 days, deploy enhanced RBAC controls across all RHACM instances to enforce principle of least privilege for ManagedClusterAddOn resource modifications and enable comprehensive audit logging for all changes to this resource. Within 30 days, establish a patch readiness process by monitoring Red Hat's security advisories for CVE-2026-66793 updates, validate patches in isolated test environments, and prepare for immediate deployment upon vendor release.

Red Hat ACM CVE-2026-66793

EUVD-2026-60951 HIGH

Improper Input Validation (CWE-20)

2026-08-18 secalert@redhat.com

GHSA-xh6j-xcjj-j38g

Privilege Escalation RCE Kubernetes Red Hat

8.8

CVSS 3.1 · Vendor: redhat

Severity by source

Vendor (redhat) PRIMARY

8.8 HIGH

AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

vuln.today AI

9.9 CRITICAL

S:C assigned independently because exploitation on the hub yields cluster-admin on separate managed clusters, crossing Kubernetes security domain boundaries.

3.1 AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H

4.0 AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H

Red Hat

8.8 HIGH

qualitative

Primary rating from Vendor (redhat).

CVSS VectorVendor: redhat

Attack Vector

Network

Attack Complexity

Low

Privileges Required

Low

User Interaction

None

Scope

Unchanged

Confidentiality

High

Integrity

High

Availability

High

Lifecycle Timeline

Analysis Generated

Aug 18, 2026 - 15:33 vuln.today

CVE Published

Aug 18, 2026 - 15:17 nvd

HIGH 8.8

DescriptionCVE.org

A flaw was found in the governance-policy-addon-controller component of Red Hat Advanced Cluster Management for Kubernetes. A user with permissions to annotate the namespaced ManagedClusterAddOn resource can override the governance-policy container image. This allows an attacker to run a controlled image with cluster-admin privileges on the managed cluster, leading to arbitrary code execution and privilege escalation.

Articles & Coverage 1

News 4 New Kubernetes Vulnerabilities - 2 Critical, 2 High Severity Aug 19, 2026

AnalysisAI

Privilege escalation and arbitrary code execution in Red Hat Advanced Cluster Management for Kubernetes (RHACM) allows an authenticated low-privilege user to hijack the governance-policy container image across managed clusters. By annotating the namespaced ManagedClusterAddOn resource - a permission that may be granted to non-administrative users - the attacker causes the governance-policy-addon-controller to deploy a malicious, attacker-controlled image running with cluster-admin privileges on every managed cluster under the hub's control. No public exploit or CISA KEV listing has been confirmed at time of analysis, but the low attack complexity and high impact across cluster boundaries make this a prioritized patching target for multi-cluster RHACM deployments.

Technical ContextAI

Red Hat ACM's governance framework enforces policy across managed Kubernetes clusters using the Open Cluster Management (OCM) add-on architecture. The governance-policy-addon-controller reconciles ManagedClusterAddOn resources on the hub cluster to deploy policy agent containers onto each spoke (managed) cluster. The root cause is CWE-20 (Improper Input Validation): the controller accepts an annotation on the ManagedClusterAddOn resource as a mechanism to override the governance-policy container image reference without sufficient authorization or integrity checks. This design flaw allows any user with Kubernetes RBAC permission to annotate that namespaced resource to substitute a legitimate image with an arbitrary one. Because the deployed image inherits cluster-admin privileges on the managed cluster - a requirement of the governance subsystem - the blast radius of the flaw crosses security domain boundaries between hub and spoke clusters.

Affected ProductsAI

The affected component is the governance-policy-addon-controller within Red Hat Advanced Cluster Management for Kubernetes. Specific affected version ranges are not enumerated in the provided CVE data; the authoritative list of affected RHACM versions is maintained in the Red Hat security advisory at https://access.redhat.com/security/cve/CVE-2026-66793 and the corresponding Bugzilla entry at https://bugzilla.redhat.com/show_bug.cgi?id=2507538. Organizations should consult those sources directly for version-specific applicability, including any errata for OpenShift-bundled ACM distributions.

RemediationAI

No exact patched version number is specified in the provided data - patch availability and exact fix versions must be confirmed via the Red Hat advisory at https://access.redhat.com/security/cve/CVE-2026-66793 and monitored via Red Hat's errata system. As an immediate compensating control, restrict Kubernetes RBAC permissions to annotate the ManagedClusterAddOn resource (specifically the patch and update verbs) exclusively to cluster-administrators and the RHACM service accounts - removing this permission from all developer, operator, or namespace-scoped roles. This trades off some operational flexibility for annotation-based workflows but directly eliminates the exploitation vector. Additionally, audit existing ManagedClusterAddOn resource annotations across all namespaces for unexpected image references, as evidence of prior exploitation. Enabling OPA/Gatekeeper or Kyverno admission control policies to reject ManagedClusterAddOn annotations containing non-approved image registries provides a defence-in-depth layer with minimal operational disruption.