Red Hat multicluster engine for Kubernetes: Server-Side Request Forgery (SSRF) (CVE-2026-66794)
Published Last modified Sources: Red Hat, CVE.org
What is affected, what to do
A flaw was found in the `cluster-proxy-addon` component of Multicluster Engine for Kubernetes. This vulnerability allows an unauthenticated attacker, who can access the user-facing route, to bypass authentication and authorization checks.
Update Red Hat multicluster engine for Kubernetes 2.10 to version 1787173361, Red Hat multicluster engine for Kubernetes 2.11 to version 1787276784, Red Hat multicluster engine for Kubernetes 2.17 to version 1786983349.
- Affected
- Red Hat multicluster engine for Kubernetes 2.10
lt *..1787173361 - Red Hat multicluster engine for Kubernetes 2.11
lt *..1787276784 - Red Hat multicluster engine for Kubernetes 2.17
lt *..1786983349 - Red Hat multicluster engine for Kubernetes 2.6
lt *..1787275318 - Red Hat multicluster engine for Kubernetes 2.8
lt *..1787275519 - Red Hat multicluster engine for Kubernetes 2.9
lt *..1787274923
- Red Hat multicluster engine for Kubernetes 2.10
- Fixed in
- Red Hat multicluster engine for Kubernetes 2.10
1787173361 - Red Hat multicluster engine for Kubernetes 2.11
1787276784 - Red Hat multicluster engine for Kubernetes 2.17
1786983349 - Red Hat multicluster engine for Kubernetes 2.6
1787275318 - Red Hat multicluster engine for Kubernetes 2.8
1787275519 - Red Hat multicluster engine for Kubernetes 2.9
1787274923
- Red Hat multicluster engine for Kubernetes 2.10
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Metrics
9.3
Priority
XIEM Effective CVSS: highest available CVSS rating from NVD and vendor data.
Source: NVD, CVSS v3
9.3
CVSS v3
Severity Critical on the scale from 0 to 10.
Source: Red Hat, CVE.org
0.6 %
EPSS score
Low — model estimates < 1% exploitation likelihood.
Source: FIRST EPSS, percentile 49.6
Show all metrics
- Severity
- Critical
Priority (0–325)
The priority score is a consolidated metric that condenses several individual signals into a single, action-guiding ranking: technical severity (CVSS), exploitation likelihood (EPSS), known-exploited status (KEV) and the context of the affected asset. The aim is to answer the only truly important question in vulnerability management: what first?
Read in glossary- 90.01 Methodology
Exploit maturity
An exploit is code or a technique that specifically uses a concrete vulnerability to force unintended behaviour — such as executing code or escalating privileges. It is the tool that turns a theoretical flaw into a practical attack.
Read in glossary- no public PoC known
XIEM Effective CVSS
XIEM® is the tiered managed-security operating model from NEOSEC and a registered trademark of NEOSEC GmbH. It extends classic SIEM — the central collection, normalisation and correlation of security-relevant events — with endpoint forensics, network visibility and deception technology, and consolidates them into three building tiers: Sentry, Orchestrate and Command.
Read in glossary- 9.3 Methodology
CVSS v3
CVSS is the globally established, open standard for assessing the technical severity of a vulnerability on a scale from 0 to 10. It describes how easily a flaw can be exploited and what damage it can cause — but not how likely its actual exploitation is. CVSS and the complementary EPSS deliberately answer different questions.
Read in glossary- 9.3
EPSS score
The EPSS score is the absolute model output for an individual vulnerability: the estimated probability of real-world exploitation within the next 30 days, expressed as a value between 0 and 1 (i.e. 0 % to 100 %). A score of 0.42 means „the model estimates a 42 % chance of real-world exploitation within 30 days“.
Read in glossary- 0.6 %
- Low — model estimates < 1% exploitation likelihood.
EPSS percentile
The EPSS percentile is the relative position of a vulnerability within all EPSS-scored CVEs, expressed as a value between 0 and 1. A percentile of 0.90 means „this CVE has a higher EPSS score than 90 % of all other scored CVEs“. Unlike the EPSS score, it is not a probability — but a positioning within a ranking.
Read in glossary- 49.6
- High — this CVE ranks above the median of all CVEs scored today (rank ≥ 36%).
KEV status
The KEV catalogue is a list maintained by the US authority CISA of vulnerabilities for which active exploitation in the wild has been confirmed. It answers not the question „how severe?“ but „is it already being attacked?“ — thereby sharply prioritising patching.
Read in glossary- —
- Published
CWE
CWE is a catalogue of typical weakness types in software and hardware — such as flawed input validation, unsafe memory handling or poor authentication. Where a CVE names a concrete vulnerability in a concrete product, a CWE describes the underlying class of defect.
Read in glossary- CWE-918
Detection rules
No NEOSEC detection rule is available for this vulnerability yet.
Classification under NIS2 and CRA
Rule-based classification from exploitation status and severity. It does not replace a case-by-case assessment.
NIS2
NIS2 is EU Directive (EU) 2022/2555 to raise the level of cybersecurity across the Union. It substantially broadens obligations compared with the first NIS directive: more sectors, mandatory risk management, staged reporting duties and personal accountability of senior management.
Read in glossary- High technical severity: assess and remediate the vulnerability in vulnerability handling under Art. 21(2)(e) NIS2 and document the decision.
CRA
The CRA is EU Regulation (EU) 2024/2847 setting horizontal cybersecurity requirements for „products with digital elements“ — from industrial controllers and software to connected consumer devices. For the first time manufacturers must ensure security across the entire product lifecycle, handle vulnerabilities and provide security updates.
Read in glossary- From 11.12.2027, Annex I Part II CRA requires manufacturers of affected products with digital elements to handle vulnerabilities without delay and provide security updates.
ISO/IEC 27001
ISO/IEC 27001 is the internationally leading standard for an information security management system (ISMS). It describes a risk-based, process-oriented framework to systematically plan, implement, review and improve information security.
Read in glossary- Control A.8.8, management of technical vulnerabilities: assess relevance to your systems, plan remediation and keep evidence.
Description
A flaw was found in the `cluster-proxy-addon` component of Multicluster Engine for Kubernetes. This vulnerability allows an unauthenticated attacker, who can access the user-facing route, to bypass authentication and authorization checks. By manipulating URL path segments, the attacker can proxy requests to arbitrary services across any managed cluster. This enables unauthorized access to internal services that would otherwise be protected, potentially leading to information disclosure or further compromise of the cluster environment.
Source: redhat_csaf, NVD (NIST), cvelistv5
Affected products
The following versions are affected. Older releases of the same product line are also vulnerable unless stated otherwise.
| Affected versions | Fixed in | ||
|---|---|---|---|
| Red Hat | multicluster engine for Kubernetes 2.10 |
|
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| Red Hat | multicluster engine for Kubernetes 2.11 |
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| Red Hat | multicluster engine for Kubernetes 2.17 |
|
|
| Red Hat | multicluster engine for Kubernetes 2.6 |
|
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| Red Hat | multicluster engine for Kubernetes 2.8 |
|
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| Red Hat | multicluster engine for Kubernetes 2.9 |
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|
Vendors and products
Weakness classes (CWE)
CWE-918Server-Side Request Forgery (SSRF)
Base
The web server receives a URL or similar request from an upstream component and retrieves the contents of this URL, but it does not sufficiently ensure that the request is being sent to the expected destination.
Entry at MITRE CWE-918
References & sources
- access.redhat.comsecurity/cve/CVE-2026-66794Vulnerability database, x_refsource_REDHAT
- bugzilla.redhat.comRHBZ#2507539Issue tracking, x_refsource_REDHAT
- access.redhat.comRHSA-2026:59556Vendor advisory, x_refsource_REDHAT
- access.redhat.comRHSA-2026:59593Vendor advisory, x_refsource_REDHAT
- access.redhat.comRHSA-2026:59557Vendor advisory, x_refsource_REDHAT
- access.redhat.comRHSA-2026:59558Vendor advisory, x_refsource_REDHAT
- access.redhat.comRHSA-2026:59559Vendor advisory, x_refsource_REDHAT
- access.redhat.comRHSA-2026:59579Vendor advisory, x_refsource_REDHAT
Changes to this CVE
Who changed this CVE and when: NVD (analysis, affected products, CVSS), the CVE publisher (CNA) and additional providers such as CISA (ADP).
Record modifiedRed Hat
1 individual change: Affected versions (publisher)
Show the original change
Individual changes of this event as published by NVD Type Action Before After Affected versions (publisher) added —Affected value modified. <a href="https://github.com/CVEProject/cvelistV5/blob/main/cves/2026/66xxx/CVE-2026-66794.json">CVE-2026-66794</a>Source identifier: secalert@redhat.com
Record modifiedRed Hat
1 individual change: Affected versions (publisher)
Show the original change
Individual changes of this event as published by NVD Type Action Before After Affected versions (publisher) added —Affected value modified. <a href="https://github.com/CVEProject/cvelistV5/blob/main/cves/2026/66xxx/CVE-2026-66794.json">CVE-2026-66794</a>Source identifier: secalert@redhat.com
Record modifiedRed Hat
1 individual change: Affected versions (publisher)
Show the original change
Individual changes of this event as published by NVD Type Action Before After Affected versions (publisher) added —Affected value modified. <a href="https://github.com/CVEProject/cvelistV5/blob/main/cves/2026/66xxx/CVE-2026-66794.json">CVE-2026-66794</a>Source identifier: secalert@redhat.com
Record modifiedRed Hat
1 individual change: Affected versions (publisher)
Show the original change
Individual changes of this event as published by NVD Type Action Before After Affected versions (publisher) added —Affected value modified. <a href="https://github.com/CVEProject/cvelistV5/blob/main/cves/2026/66xxx/CVE-2026-66794.json">CVE-2026-66794</a>Source identifier: secalert@redhat.com
Record modifiedRed Hat
1 individual change: Affected versions (publisher)
Show the original change
Individual changes of this event as published by NVD Type Action Before After Affected versions (publisher) added —Affected value modified. <a href="https://github.com/CVEProject/cvelistV5/blob/main/cves/2026/66xxx/CVE-2026-66794.json">CVE-2026-66794</a>Source identifier: secalert@redhat.com
Show 3 older changes
Record modifiedRed Hat
New references:Show 2 original changes
Individual changes of this event as published by NVD Type Action Before After Reference added —https://access.redhat.com/errata/RHSA-2026:59593Affected versions (publisher) changed multicluster engine for Kubernetes 2.11, Multicluster Engine for Kubernetesmulticluster engine for Kubernetes 2.11, multicluster engine for Kubernetes 2.17, Multicluster Engine for KubernetesSource identifier: secalert@redhat.com
Record modifiedRed Hat
New references:Show 2 original changes
Individual changes of this event as published by NVD Type Action Before After Reference added —https://access.redhat.com/errata/RHSA-2026:59556Affected versions (publisher) changed Multicluster Engine for Kubernetes, Multicluster Engine for Kubernetesmulticluster engine for Kubernetes 2.11, Multicluster Engine for KubernetesSource identifier: secalert@redhat.com
ReceivedRed Hat
CVSS V3.1: AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:L/A:N
Weakness type: CWE-918
Description added or changed
Show 6 original changes
Individual changes of this event as published by NVD Type Action Before After Affected versions (publisher) added —Multicluster Engine for Kubernetes, Multicluster Engine for KubernetesDescription added —A flaw was found in the `cluster-proxy-addon` component of Multicluster Engine for Kubernetes. This vulnerability allows an unauthenticated attacker, who can access the user-facing route, to bypass authentication and authorization checks. By manipulating URL path segments, the attacker can proxy requests to arbitrary services across any managed cluster. This enables unauthorized access to internal services that would otherwise be protected, potentially leading to information disclosure or further compromise of the cluster environment.CVSS added —AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:L/A:NWeakness type (CWE) added —CWE-918Reference added —https://access.redhat.com/security/cve/CVE-2026-66794Reference added —https://bugzilla.redhat.com/show_bug.cgi?id=2507539Source identifier: secalert@redhat.com
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<a href="https://intel.neosec.eu/en/cve/CVE-2026-66794"><img src="https://intel.neosec.eu/badge/cve/CVE-2026-66794.svg?lang=en" alt="CVE-2026-66794 – NEOSEC Intel" height="20"></a>