Rhacm: open cluster management (ocm): cross-cluster privilege escalation via improper kubernetes client certificate renewal validation

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Summary

CVECVE-2026-4740
StatePUBLISHED
Assignerredhat
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-04-07 15:17:46 UTC
Updated2026-04-08 21:27:00 UTC
DescriptionA 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.

Risk And Classification

Primary CVSS: v3.1 8.2 HIGH from [email protected]

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

EPSS: 0.000080000 probability, percentile 0.007000000 (date 2026-04-13)

Problem Types: CWE-295 | CWE-295 Improper Certificate Validation

VersionSourceTypeScoreSeverityVector
3.1[email protected]Primary8.2HIGHCVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:C/C:H/I:H/A:H
3.1CNACVSS8.2HIGHCVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:C/C:H/I:H/A:H

CVSS v3.1 Breakdown

Attack Vector
Local
Attack Complexity
Low
Privileges Required
High
User Interaction
None
Scope
Changed
Confidentiality
High
Integrity
High
Availability
High

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

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Red Hat Multicluster Engine For Kubernetes Not specified Not specified
CNA Red Hat Multicluster Engine For Kubernetes Not specified Not specified

References

ReferenceSourceLinkTags
bugzilla.redhat.com/show_bug.cgi [email protected] bugzilla.redhat.com
blog.arfevrier.fr/open-cluster-management-cross-cluster-escape [email protected] blog.arfevrier.fr
access.redhat.com/security/cve/CVE-2026-4740 [email protected] access.redhat.com
CVE Program record CVE.ORG www.cve.org canonical
NVD vulnerability detail NVD nvd.nist.gov canonical, analysis

Vendor Comments And Credit

Discovery Credit

CNA: Red Hat would like to thank Arnaud FEVRIER (Orange) for reporting this issue. (en)

Additional Advisory Data

SourceTimeEvent
CNA2026-03-24T03:18:24.150ZReported to Red Hat.
CNA2026-04-07T14:00:35.240ZMade public.

Workarounds

CNA: Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base, or stability.

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