---
id: CVE-2026-4740
title: >-
  A flaw was found in Open Cluster Management (OCM), the technology underlying
  Red Hat Advanced Cluster Management (ACM)
summary: >-
  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…
severity: high
cvss: 8.2
cvssVector: 'CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:C/C:H/I:H/A:H'
cwe:
  - CWE-295
vendor: redhat
product: advanced_cluster_management_for_kubernetes
affected:
  - advanced_cluster_management_for_kubernetes
published: '2026-04-07'
updated: '2026-09-08'
sourceUpdated: '2026-09-08T12:16:54.783'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-4740'
references:
  - url: 'https://access.redhat.com/errata/RHSA-2026:11414'
    label: secalert@redhat.com
  - url: 'https://access.redhat.com/errata/RHSA-2026:13542'
    label: secalert@redhat.com
  - url: 'https://access.redhat.com/errata/RHSA-2026:13853'
    label: secalert@redhat.com
  - url: 'https://access.redhat.com/errata/RHSA-2026:8218'
    label: secalert@redhat.com
  - url: 'https://access.redhat.com/errata/RHSA-2026:9848'
    label: secalert@redhat.com
  - url: 'https://access.redhat.com/security/cve/CVE-2026-4740'
    label: secalert@redhat.com
  - url: 'https://blog.arfevrier.fr/open-cluster-management-cross-cluster-escape/'
    label: secalert@redhat.com
  - url: 'https://bugzilla.redhat.com/show_bug.cgi?id=2450590'
    label: secalert@redhat.com
  - url: 'https://access.redhat.com/errata/RHSA-2026:11414'
    label: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
  - url: 'https://access.redhat.com/errata/RHSA-2026:13542'
    label: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
  - url: 'https://access.redhat.com/errata/RHSA-2026:13853'
    label: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
  - url: 'https://access.redhat.com/errata/RHSA-2026:8218'
    label: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
  - url: 'https://access.redhat.com/errata/RHSA-2026:9848'
    label: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
  - url: 'https://access.redhat.com/security/cve/CVE-2026-4740'
    label: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
  - url: 'https://bugzilla.redhat.com/show_bug.cgi?id=2450590'
    label: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
  - url: >-
      https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-4740.json
    label: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
  - url: 'https://www.cve.org/CVERecord?id=CVE-2026-4740'
  - url: 'https://nvd.nist.gov/vuln/detail/CVE-2026-4740'
tags:
  - nvd
  - cve.org
  - csaf
  - vex
  - red-hat
ssvc:
  exploitation: none
  automatable: 'no'
  technicalImpact: total
  timestamp: '2026-04-09T14:40:37.454585Z'
epss: 0.00148
epssPercentile: 0.04425
ingestedAt: '2026-07-13T17:27:58.720Z'
patched:
  - multicluster_engine_for_kubernetes 2.11
  - multicluster_engine_for_kubernetes 2.1
  - multicluster_engine_for_kubernetes 2.6
  - multicluster_engine_for_kubernetes 2.8
  - multicluster_engine_for_kubernetes 2.9
---

## Overview

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.

## Affected

- `advanced_cluster_management_for_kubernetes`

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.

## Vendor advisories

- **RHSA-2026:13853** · Red Hat · fixed in: multicluster engine for Kubernetes 2.11 · released 2026-05-05 · [advisory](https://access.redhat.com/errata/RHSA-2026:13853)
- **RHSA-2026:13542** · Red Hat · fixed in: multicluster engine for Kubernetes 2.1 · released 2026-05-04 · [advisory](https://access.redhat.com/errata/RHSA-2026:13542)
- **RHSA-2026:9848** · Red Hat · fixed in: multicluster engine for Kubernetes 2.6 · released 2026-04-22 · [advisory](https://access.redhat.com/errata/RHSA-2026:9848)
- **RHSA-2026:8218** · Red Hat · fixed in: multicluster engine for Kubernetes 2.8 · released 2026-04-15 · [advisory](https://access.redhat.com/errata/RHSA-2026:8218)
- **RHSA-2026:11414** · Red Hat · fixed in: multicluster engine for Kubernetes 2.9 · released 2026-04-28 · [advisory](https://access.redhat.com/errata/RHSA-2026:11414)
- **Red Hat VEX** · Important · affected: Multicluster Engine for Kubernetes · updated 2026-09-08 · [vex](https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-4740.json)