CVE-2026-4740

A flaw was found in Open Cluster Management (OCM), the technology underlying Red Hat Advanced Cluster Management (ACM). Improper validation of Kubernetes client certificate renewal allows a managed cluster administrator to forge a client certificate that can be approved by the OCM controller. This enables cross-cluster privilege escalation and may allow an attacker to gain control over other managed clusters, including the hub cluster.

What this means for your business

It affects Redhat Advanced Cluster Management For Kubernetes. It matters if your company, or a supplier that handles your data, runs it.
Code showing how to exploit it has been published, but real attacks have not been confirmed.
An attacker can use it only with access to the machine itself, with an administrator login, and without anyone at your company clicking anything.
FIRST's prediction model gives it a 0.1% chance of attack attempts being seen in the next 30 days, ranking above 4% of all known flaws.

What to do

1Check whether your company or your suppliers run Redhat Advanced Cluster Management For Kubernetes, and which version. The affected versions are listed further down this page.
2If you do, apply the vendor's fix. A patch or vendor advisory has been published.

Not sure if your company is exposed?

Fastnexa’s certified penetration testers can check whether attackers could use this flaw, or others like it, against your websites, apps and network. The full test is free for our first 10 founding clients until 31 December 2026.

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Scoring

CVSS: 8.2 (v3.1)
Vector: CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:C/C:H/I:H/A:H
Weakness: CWE-295
Assigned by: secalert@redhat.com

Dates

Published: 2026-04-07
Last modified: 2026-09-08
Sources: NVD

Affected products

Redhat Advanced Cluster Management For Kubernetesall versions

As listed in the NVD configuration data. Not a statement about your estate.