CVE-2026-4740: Red Hat multicluster engine for Kubernetes 2.1 · Improper Certificate Validation
Affects Red Hat multicluster engine for Kubernetes 2.1Source CVE Database V5
Not known to be exploited · CVSS 8.2 High.
Data as of 30 Oct 2026, 11:52 UTC
- EPSS
- 0.1% chance of exploitation in 30 days – higher than 4% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:C/C:H/I:H/A:HExploitation evidence
Disclosed: evidence found.
CVE published 7 Apr 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors
A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 30 Oct 2026.
What to do
Affected software
| Product | Affected | Fixed in |
|---|---|---|
| Red Hatmulticluster engine for Kubernetes 2.1 | Affected– | Fixed in– |
| Red Hatmulticluster engine for Kubernetes 2.11 | Affected– | Fixed in– |
| Red Hatmulticluster engine for Kubernetes 2.6 | Affected– | Fixed in– |
| Red Hatmulticluster engine for Kubernetes 2.8 | Affected– | Fixed in– |
| Red Hatmulticluster engine for Kubernetes 2.9 | Affected– | Fixed in– |
| Red HatMulticluster Engine for Kubernetes | Affected– | Fixed in– |
AI-suggested
As per the Red Hat advisory, no mitigation or patch currently meets the criteria for ease of use, deployment, applicability, or stability. Users are advised to monitor Red Hat advisories for updates. Customers with a Technical Account Manager (TAM) or RHEL Security Select Add-on can consult directly with Red Hat for guidance. Until a fix is available, limiting administrative privileges and closely controlling managed cluster administrator access may reduce risk, but no official mitigation is provided.
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.
References
- access.redhat.com/security/cve/CVE-2026-4740 (opens in a new tab)
- blog.arfevrier.fr/open-cluster-management-cross-cluster-escape/ (opens in a new tab)
- bugzilla.redhat.com/show_bug.cgi?id=2450590 (opens in a new tab)
- security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-4740.json (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:11414 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:13853 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:9848 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:13542 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:8218 (opens in a new tab)