External risk intelligence

Red Hat Advanced Cluster Management Subscription Controller Privilege Escalation

CVE advisorySeverity: CRITICAL (CVSS 9.9)

CVE-2026-10090

The vulnerability exists within the internal management plane of a Kubernetes cluster-management tool. While it involves network-reachable components, these administrative controllers are typically deployed within private, secured environments rather than exposed directly to the public internet.

Privilege Escalation

Halo Surface Signal: 2 out of 5 — less likely to be public-facing.

External exposure likelihood

Horizon Alert

Summary of the vulnerability and why it matters

A security flaw in Red Hat Advanced Cluster Management for Kubernetes allows a user with moderate privileges to gain full administrative control of the cluster by crafting a malicious application update. This enables them to deploy unauthorized cluster-wide configurations and elevate their access.

Malicious updates can grant full cluster control.
Confirms administrative oversight of application deployment.
Validate controls and assess exposure to this threat.

Attack Path

How an attacker could exploit the issue

An attacker with specific permissions within a Red Hat Advanced Cluster Management hub namespace can create a subscription that points to a malicious Helm repository. The system's subscription controller then fetches and deploys the Helm chart using elevated privileges, overriding namespace restrictions. This allows the attacker to deploy cluster-wide resources, ultimately granting them full administrative control of the Kubernetes cluster.

Requires namespace-scoped "edit" privileges.
Triggered by creating a malicious subscription.
Results in cluster-admin privilege escalation.

Live Threat

Current exploitation, exposure, and threat context

When a user with sufficient privileges creates a subscription, the application subscription controller may fetch and apply Helm chart contents with elevated authority. This could lead to the inclusion of cluster-scoped resources, potentially allowing for privilege escalation.

Cluster-wide administrative privileges.
Controller applies unauthorized resources.
Complete cluster control and compromise.

Operational Fix

Recommended remediation, mitigation, and detection steps

Red Hat Advanced Cluster Management for Kubernetes administrators and platform teams are responsible for addressing this vulnerability. The first practical step is to identify all instances of the affected controller, confirm its reachability and criticality, and then determine the accountable owner to plan remediation based on the assessed risk.

Platform or application owners should manage this issue.
Verify subscription controller's role and namespace restrictions.
Plan remediation for affected subscriptions and namespaces.

Supplementary metadata

CVSS vector

Validate whether this threat affects your internet-facing exposure.

Halo Threat Intelligence helps prioritize remediation with Halo Surface Signal and H/A/L/O context. Start exposure validation with a free external attack surface trial.

Free EASM Trial See How Signal Works

Frequently asked questions

What is Red Hat Advanced Cluster Management for Kubernetes?

It is a management platform used to oversee multiple Kubernetes clusters from a single central hub. It simplifies tasks like application deployment and governance across diverse environments. The affected 'multicluster-operators-subscription' component specifically handles the delivery of applications—such as Helm charts—from repositories to those managed clusters, ensuring software stays consistent across a large-scale infrastructure.

What does CWE-267 mean for CVE-2026-10090?

This vulnerability is classified as CWE-267, which refers to 'Privilege Issue During Operating System Code Execution' or, more broadly, improper privilege management. In this specific case, it means the software performs tasks with higher permissions than the user who requested them. The controller acts on behalf of the system with elevated authority, failing to verify if the user possesses the proper administrative role before deploying requested resources.

How is this vulnerability triggered?

An attacker must have existing 'edit' privileges within an ACM hub namespace. They trigger the flaw by creating a Subscription resource that points to a malicious Helm repository they control. It is important to note that simply having access to a namespace does not trigger the bug; the vulnerability requires the specific action of configuring a subscription that forces the controller to process and apply unauthorized, cluster-scoped resources outside of the intended namespace boundaries.

Is my cluster at risk based on Halo Surface Signal?

Halo Surface Signal identifies this as 'Unlikely' because the affected controller functions within the internal management plane of your infrastructure. While the underlying components have network connectivity, these administrative controllers are generally kept in private, secured environments. You should primarily worry if your ACM hub is accessible beyond your internal team or if you have untrusted users with 'edit' rights in your hub namespaces.

What should I do first to address CVE-2026-10090?

Start by identifying all deployed instances of the subscription controller and reviewing who has 'edit' access within your ACM hub namespaces. You should verify that current subscription configurations align with your security policies and ensure that no unauthorized or unexpected Helm repositories are being used. Coordinate with your platform and application owners to confirm that resource deployments are restricted to their intended, isolated namespaces while awaiting official updates.

References

Written by Nicholas Merritt

Nicholas Merritt is VP of Security Solutions at Halo Security. With more than 25 years across application security, vulnerability prioritization, and offensive security, he helps teams translate threat data into practical exposure validation and remediation focus. He authors Halo Threat Intelligence CVE advisories using Halo Surface Signal and H/A/L/O context to prioritize internet-facing risk.