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.
CVE-2026-4740
“—” beside the score: it is equal to the CVSS score beside it.
This high-severity CVE scores 8.2 under the CNA's CVSS (NVD's own analysis pending). EPSS exploit probability: 0.2% (5th percentile of EPSS-scored CVEs). No GitHub Security Advisory CVSS is on record for this CVE.
- High severity, but no confirmed exploitation yet
A fix is available — apply it.
- CVSS v3
- 8.2
- EG Score
- 8.2HIGHmedium confidence
- EG Risk
- 37EG Risk 37/100
EG Risk is EchelonGraph's 0–100 priority score. It fuses impact severity (EG Severity, the CVSS base score, never the KEV-floored or EPSS-lifted EG Score) with real-world exploitation and automatability, under weights EchelonGraph set by hand, so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner.
How it’s computed (value × EchelonGraph’s weight)Severity82% × 45%Impact severity (EG Severity): CVSS 8.2 of 10. Never the KEV-floored or EPSS-lifted EG Score.Exploitation0.2% × 40%FIRST EPSS: the 30-day exploitation probability when EchelonGraph scored this CVE.Automatability0% × 15%CISA's SSVC Automatable value: no (Vulnrichment).SSVC (CISA's decision table, applied by EchelonGraph): Track at low or medium mission impact; Track* at high (mission-essential systems).Exploitation none (CISA Vulnrichment) · Automatable no (CISA Vulnrichment) · Technical impact total (CISA Vulnrichment). All three are CISA's SSVC values (Vulnrichment). EchelonGraph applied CISA's decision table to them; CISA publishes SSVC inputs and the table, not a decision for each CVE.Action: A fix is available. Apply it within your standard update timelines. - EPSS PROB
- 0.2%
- EPSS %ILE
- 5th
- KEV
- Not listed
What the EG score is made of (scorer v4.0: the three questions the 0–10 score mixes, published apart · methodology)
The EG score (8.2): severity, escalated by confirmed exploitation. This CVE's 8.2 is its impact severity (EG Severity), not escalated.
- EG Severity
- 8.2 HIGHCVSS-B, impact only: no KEV listing, EPSS or EG-KEV tier raises it.the CNA's CVSS · CVSS v3.0 or v3.1
- EG Likelihood
- 0.2% within 30 daysSource: FIRST EPSS (model v2026.06.15, score date 2026-10-17). FIRST's exploitation probability, not an EchelonGraph model.
- Confirmed exploitation
- None on record (CISA KEV, EG-KEV Tier 1)Reported apart from the likelihood: an observed fact, not a probability.
- EG Priority
- SSVC Track at medium mission impactTrack at low or medium mission impact; Track* at high (mission-essential systems).CISA BOD 26-04: 14 days if the affected system is publicly exposed; Fix on system upgrade if it is not.Each input and its source: the SSVC and BOD 26-04 blocks below.
SSVC (CISA's decision table, applied by EchelonGraph)Track at low or medium mission impact; Track* at high (mission-essential systems).
A fix is available. Apply it within your standard update timelines.
Exploitation none (CISA Vulnrichment) · Automatable no (CISA Vulnrichment) · Technical impact total (CISA Vulnrichment). All three are CISA's SSVC values (Vulnrichment). EchelonGraph applied CISA's decision table to them; CISA publishes SSVC inputs and the table, not a decision for each CVE. Mission impact is CISA's Mission & Well-being decision point, and only you can judge it. CISA's table makes it high when Mission Prevalence is Essential — the vulnerable component "directly provides capabilities that constitute at least one MEF for at least one entity" (MEF: mission essential function) — or when Public Well-Being Impact is Irreversible: "multiple fatalities are likely", the cyber-physical system "is likely lost or destroyed", "extreme or serious externalities" are imposed on other parties, or social systems such as elections or the financial grid "are destabilized and potentially collapse". CISA's decision table
BOD 26-04 (CISA's remediation timeline, Table 1)14 days if the affected system is publicly exposed; Fix on system upgrade if it is not.
In CISA KEV no (CISA's KEV catalog) · Automatable no (CISA Vulnrichment) · Technical impact total (CISA Vulnrichment). Whether your system is publicly exposed is yours to answer. BOD 26-04 binds US Federal Civilian Executive Branch agencies; for anyone else it is CISA's published timeline, a reference rather than an obligation. The directive · how EchelonGraph applies it
Published
April 7, 2026
Last Modified
September 9, 2026
Advisory Details (3)
Auto-updated May 4, 20262450590 – (CVE-2026-4740) CVE-2026-4740 rhacm: Open Cluster Management (OCM): Cross-cluster privilege escalation via improper Kubernetes client certificate renewal validation
https://bugzilla.redhat.com/show_bug.cgi?id=2450590CVE-2026-4740 - Cross-cluster escalation in Red Hat ACM and Open Cluster Management
https://blog.arfevrier.fr/open-cluster-management-cross-cluster-escape/Vendor Advisories for CVE-2026-4740(5)
These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.
- RHSA-2026:13853Red Hat Product SecurityHigh
Red Hat Security Advisory: multicluster engine for Kubernetes v2.11.1 security update
- RHSA-2026:13542Red Hat Product SecurityHigh
Red Hat Security Advisory: multicluster engine for Kubernetes v2.10.2 security update
- RHSA-2026:11414Red Hat Product SecurityHigh
Red Hat Security Advisory: multicluster engine for Kubernetes v2.9.3 security update
- RHSA-2026:9848Red Hat Product SecurityHigh
Red Hat Security Advisory: multicluster engine for Kubernetes v2.6.10 security update
- RHSA-2026:8218Red Hat Product SecurityHigh
Red Hat Security Advisory: multicluster engine for Kubernetes v2.8.5 security update
Patch Availability(5)
| Vendor / Ecosystem | Fix (by version range) / Patch | Released | Source |
|---|---|---|---|
| redhat | multicluster-engine/registration-rhel9:1777478390 | 2026-05-05 | redhat |
| redhat | multicluster-engine/registration-rhel9:1776881164 | 2026-05-04 | redhat |
| redhat | multicluster-engine/registration-rhel9:1776445095 | 2026-04-28 | redhat |
| redhat | multicluster-engine/registration-rhel9:1775977180 | 2026-04-22 | redhat |
| redhat | multicluster-engine/registration-rhel9:1775638726 | 2026-04-15 | redhat |
Patches are aggregated from vendor advisories (Red Hat, Microsoft, Cisco, GitHub) and package ecosystems (OSV, GHSA). Multiple rows for the same upstream release have been deduplicated.
Affected Packages
(1 across 1 ecosystem)
Go(1)
| Package | Vulnerable range | Fix by version range | Dependents |
|---|---|---|---|
| open-cluster-management.io/ocm | — |
| — |
Weakness Classification(1)
MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.
Data Freshness Timeline
(refreshed 10× in last 7d / 32× in last 30d)
Each row is a time one of our pipelines fetched, updated or re-scored this CVE. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. An arrow marks a change the record states ("CVSS v3 → 9.1"); EPSS and GHSA rows show the values recorded at that time, not what changed (EPSS values are rounded; hover one for the exact figures). Most recent first.
Showing the most recent 100 of 263 refreshes on record for this CVE.
A repeat, a row identical to one the same pipeline wrote less than 10 seconds earlier, is not a separate refresh and is not counted. None are among the latest 100 rows. The 163 oldest rows on record are not shown and were not checked, so the counts can still include repeats.
- 2026-10-21 16:33 UTCEPSS rescoreEPSS 0.2% · 5th percentile
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- 2026-10-18 03:36 UTCEG score recompute
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- 2026-10-17 12:47 UTCEG score recompute
- 2026-10-17 12:47 UTCVendor advisory
- 2026-10-16 16:42 UTCEPSS rescoreEPSS 0.2% · 5th percentile
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- 2026-10-11 13:49 UTCEPSS rescoreEPSS 0.2% · 5th percentile
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- 2026-09-09 12:40 UTCVendor advisory
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- 2026-08-23 00:19 UTCEPSS rescoreEPSS 0.1% · 4th percentile
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Related CVEs(same product + same vendor + same CWE)
Same vendor
10 shownredhat:RHSA-2026:11414 · redhat:RHSA-2026:13542 · redhat:RHSA-2026:8218
Frequently asked(5)
What is CVE-2026-4740?
When was CVE-2026-4740 made public?
Is CVE-2026-4740 actively exploited?
What is the CVSS score of CVE-2026-4740?
How do I remediate CVE-2026-4740?
Dependency Blast Radius
See which npm, PyPI, Go, and Maven packages are affected by CVE-2026-4740
Is Your Infrastructure Affected by CVE-2026-4740?
EchelonGraph automatically scans your cloud infrastructure and maps CVE exposure using blast radius analysis.