# CVE-2026-4740: Open Cluster Management (OCM): Cross-cluster privilege escalation via improper Kubernetes client certificate renewal validation

> A managed cluster administrator can forge client certificates to escalate privileges and control other managed clusters, including the hub cluster.

- **Severity:** High 8.2 (`CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:C/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** An administrator
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 7 Apr 2026
- **Updated:** 9 Sep 2026
- **Also known as:** GHSA-q4gv-pjmh-c735, GO-2026-5564

## What is CVE-2026-4740?

CVE-2026-4740 is a high-severity vulnerability in Red Hat Multicluster Engine for Kubernetes, published on 7 Apr 2026. It can only be exploited from the same machine or local network, with no action from the victim.

### Official 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.

Weakness: CWE-295 (Improper Certificate Validation)

## Which versions are affected by CVE-2026-4740?

3 open source packages ship an affected version, including open-cluster-management.io/ocm. It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `open-cluster-management.io/ocm` | Go | All versions | 1.2.1 |
| `open-cluster-management.io/ocm` | Go | All versions | 1.2.1 |
| `open-cluster-management.io/ocm` | Go | All versions | 1.2.1 |

Products: Redhat Advanced Cluster Management for Kubernetes.

## How do I fix CVE-2026-4740?

Upgrade open-cluster-management.io/ocm to 1.2.1 or later.

## Is CVE-2026-4740 being exploited?

There is no known exploitation of CVE-2026-4740 in the wild and no public exploit code.

## Other vulnerabilities in Red Hat Multicluster Engine for Kubernetes

- [CVE-2023-3027](https://insights.sbomify.com/CVE-2023-3027/): Privilege escalation in RHACM (high 7.8)
- [CVE-2022-3841](https://insights.sbomify.com/CVE-2022-3841/): Server-side request forgery in RHACM (high 7.8)
- [CVE-2026-71474](https://insights.sbomify.com/CVE-2026-71474/): Insights-client-rhel9: insights-client: pull-secret bearer token written to logs on non-200 ccx response (high 7.1)
- [CVE-2026-71475](https://insights.sbomify.com/CVE-2026-71475/): Insights-client-rhel9: insights-client: spoke-controlled clusterid injected unencoded into insights api url path (medium 6.8)
- [CVE-2026-71846](https://insights.sbomify.com/CVE-2026-71846/): Insights-client: insights-client: clusterrole grants cluster-wide secrets get/list/watch beyond least privilege (medium 6.5)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-4740 and fix it if it is affected.

What it is: CVE-2026-4740 is a high-severity vulnerability in Red Hat Multicluster Engine for Kubernetes, published on 7 Apr 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-4740 in the wild and no public exploit code.

Affected packages and fixed versions:
- open-cluster-management.io/ocm (Go): affected all versions; fixed in 1.2.1
- open-cluster-management.io/ocm (Go): affected all versions; fixed in 1.2.1
- open-cluster-management.io/ocm (Go): affected all versions; fixed in 1.2.1

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-4740/ (Markdown: https://insights.sbomify.com/CVE-2026-4740/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-4740
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-4740
- OSV: https://osv.dev/vulnerability/CVE-2026-4740

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-4740/
Summaries are generated and may contain mistakes; the official description above is the record.