CVE-2026-4740

High

Published: 07 April 2026

Published

07 April 2026

Modified

08 April 2026

KEV Added

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Patch

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CVSS Score 8.2 CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:C/C:H/I:H/A:H

EPSS Score 0.0001 0.9th percentile

Risk Priority 16 60% EPSS · 20% KEV · 20% CVSS

Summary

CVE-2026-4740 is a high-severity Improper Certificate Validation (CWE-295) vulnerability in Arfevrier (inferred from references). Its CVSS base score is 8.2 (High).

Operationally, exploitation aligns with the MITRE ATT&CK technique Exploitation for Privilege Escalation (T1068); ranked at the 0.9th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.

The strongest mitigations our analysis identified are NIST 800-53 IA-5 (Authenticator Management) and SC-17 (Public Key Infrastructure Certificates).

Threat & Defense at a Glance

What attackers do: exploitation maps to Exploitation for Privilege Escalation (T1068). What defenders deploy: see the NIST 800-53 controls recommended below.

Threat & Defense Details

Mitigating Controls (NIST 800-53 r5)AI

IA-5 Authenticator Management good match

prevent

Requires validation and proper management of authenticators like client certificates prior to use, directly preventing forgery and improper renewal approval in OCM.

SC-17 Public Key Infrastructure Certificates good match

prevent

Mandates management and validation of PKI certificates in accordance with defined requirements, addressing the improper validation flaw in Kubernetes client certificate renewal.

SI-2 Flaw Remediation good match

prevent

Ensures timely identification, reporting, and correction of software flaws such as improper certificate validation through patching, mitigating cross-cluster privilege escalation.

MITRE ATT&CK Enterprise TechniquesAI

T1068 Exploitation for Privilege Escalation Privilege Escalation

Adversaries may exploit software vulnerabilities in an attempt to elevate privileges.

attack.mitre.org →

Why these techniques?

The vulnerability enables cross-cluster privilege escalation by allowing a managed cluster administrator to forge an approved client certificate, granting unauthorized control over the hub cluster and other managed clusters.

Confidence: HIGH · MITRE ATT&CK Enterprise v18.1

NVD Description

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.

Deeper analysisAI

CVE-2026-4740 is a vulnerability in Open Cluster Management (OCM), the technology underlying Red Hat Advanced Cluster Management (ACM). The flaw stems from improper validation of Kubernetes client certificate renewal, which allows a managed cluster administrator to forge a client certificate that can be approved by the OCM controller. Published on 2026-04-07, it has a CVSS score of 8.2 (CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:C/C:H/I:H/A:H) and is associated with CWE-295.

A managed cluster administrator can exploit this vulnerability locally with high privileges but low complexity and no user interaction required. Successful exploitation enables cross-cluster privilege escalation, potentially allowing the attacker to gain control over other managed clusters, including the hub cluster.

Red Hat's security advisory at https://access.redhat.com/security/cve/CVE-2026-4740, a related blog post at https://blog.arfevrier.fr/open-cluster-management-cross-cluster-escape/, and Bugzilla entry https://bugzilla.redhat.com/show_bug.cgi?id=2450590 provide details on patches and mitigation steps.