HighCVE-2026-4740

    Red Hat multicluster engine for Kubernetes: Improper Certificate Validation (CVE-2026-4740)

    Published Last modified Sources: Red Hat, EUVD, CVE.org, OSV

    What is affected, what to do

    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.

    Update Red Hat multicluster engine for Kubernetes 2.1 to version 1776881164, Red Hat multicluster engine for Kubernetes 2.11 to version 1777478390, Red Hat multicluster engine for Kubernetes 2.6 to version 1775977180.

    Affected
    • Red Hat multicluster engine for Kubernetes 2.1 lt *..1776881164
    • Red Hat multicluster engine for Kubernetes 2.11 lt *..1777478390
    • Red Hat multicluster engine for Kubernetes 2.6 lt *..1775977180
    • Red Hat multicluster engine for Kubernetes 2.8 lt *..1775638726
    • Red Hat multicluster engine for Kubernetes 2.9 lt *..1776445095
    Fixed in
    • Red Hat multicluster engine for Kubernetes 2.1 1776881164
    • Red Hat multicluster engine for Kubernetes 2.11 1777478390
    • Red Hat multicluster engine for Kubernetes 2.6 1775977180
    • Red Hat multicluster engine for Kubernetes 2.8 1775638726
    • Red Hat multicluster engine for Kubernetes 2.9 1776445095

    Not sure whether and how you are affected? Ask a question about this vulnerability

    Metrics

    8.2

    Priority

    XIEM Effective CVSS: highest available CVSS rating from NVD and vendor data.

    Source: NVD, CVSS v3

    8.2

    CVSS v3

    Severity High on the scale from 0 to 10.

    Source: Red Hat, EUVD, CVE.org, OSV

    0.2 %

    EPSS score

    Low — model estimates < 1% exploitation likelihood.

    Source: FIRST EPSS, percentile 4.0

    Show all metrics
    Severity
    High
    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
    57.16 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
    8.2 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
    8.2
    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
    0.2 %
    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
    4.0
    Low — this CVE sits in the lower 10% of all CVEs scored today.
    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-295, CWE-295

    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 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.

    Source: redhat_csaf, ENISA EUVD, NVD (NIST), OSV (Open Source Vulnerabilities), CVE.org (MITRE), cvelistv5

    Affected products

    The following versions are affected. Older releases of the same product line are also vulnerable unless stated otherwise.

    Affected products
    Affected versionsFixed in
    Red HatMulticluster Engine for Kubernetes
    • —
    • —
    Red Hatmulticluster engine for Kubernetes 2.1
    • < 1776881164
    • 1776881164
    Red Hatmulticluster engine for Kubernetes 2.11
    • < 1777478390
    • 1777478390
    Red Hatmulticluster engine for Kubernetes 2.6
    • < 1775977180
    • 1775977180
    Red Hatmulticluster engine for Kubernetes 2.8
    • < 1775638726
    • 1775638726
    Red Hatmulticluster engine for Kubernetes 2.9
    • < 1776445095
    • 1776445095
    redhatadvanced_cluster_management_for_kubernetes
    • —
    • —
    goopen-cluster-management.io/ocm
    • —
    • —

    Vendors and products

    Weakness classes (CWE)

    • CWE-295Improper Certificate Validation

      Base

      The product does not validate, or incorrectly validates, a certificate.

      Entry at MITRE CWE-295

    • CWE-295Improper Certificate Validation

      Base

      The product does not validate, or incorrectly validates, a certificate.

      Entry at MITRE CWE-295

    References & sources

    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).

    1. Record modifiedRed Hat

      1 individual change: Affected versions (publisher)

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      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
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      Affected value modified. <a href="https://github.com/CVEProject/cvelistV5/blob/main/cves/2026/4xxx/CVE-2026-4740.json">CVE-2026-4740</a>

      Source identifier: secalert@redhat.com

    2. Record modifiedRed Hat

      1 individual change: Affected versions (publisher)

      Show the original change
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Affected versions (publisher)added
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      Affected value modified. <a href="https://github.com/CVEProject/cvelistV5/blob/main/cves/2026/4xxx/CVE-2026-4740.json">CVE-2026-4740</a>

      Source identifier: secalert@redhat.com

    3. Record modifiedRed Hat

      1 individual change: Affected versions (publisher)

      Show the original change
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Affected versions (publisher)added
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      Affected value modified. <a href="https://github.com/CVEProject/cvelistV5/blob/main/cves/2026/4xxx/CVE-2026-4740.json">CVE-2026-4740</a>

      Source identifier: secalert@redhat.com

    4. Record modifiedRed Hat ADP

      1 individual change: Affected versions (publisher)

      Show the original change
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Affected versions (publisher)added
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      Affected value modified. <a href="https://github.com/CVEProject/cvelistV5/blob/main/cves/2026/4xxx/CVE-2026-4740.json">CVE-2026-4740</a>

      Source identifier: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c

    5. Record modifiedRed Hat

      Show 20 original changes
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Affected versions (publisher)added
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      Affected value modified. <a href="https://github.com/CVEProject/cvelistV5/blob/main/cves/2026/4xxx/CVE-2026-4740.json">CVE-2026-4740</a>
      Referenceadded
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      https://access.redhat.com/errata/RHSA-2026:11414
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      https://access.redhat.com/errata/RHSA-2026:13542
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      https://access.redhat.com/errata/RHSA-2026:13853
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      https://access.redhat.com/errata/RHSA-2026:8218
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      https://access.redhat.com/errata/RHSA-2026:9848
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      https://access.redhat.com/security/cve/CVE-2026-4740
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      https://blog.arfevrier.fr/open-cluster-management-cross-cluster-escape/
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      https://bugzilla.redhat.com/show_bug.cgi?id=2450590
      Referenceremoved
      https://access.redhat.com/errata/RHSA-2026:11414
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      https://access.redhat.com/errata/RHSA-2026:13542
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      https://access.redhat.com/errata/RHSA-2026:13853
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      https://access.redhat.com/errata/RHSA-2026:8218
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      https://access.redhat.com/errata/RHSA-2026:9848
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      https://access.redhat.com/security/cve/CVE-2026-4740
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      https://blog.arfevrier.fr/open-cluster-management-cross-cluster-escape/
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      https://bugzilla.redhat.com/show_bug.cgi?id=2450590
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      Reference typeremoved
      https://access.redhat.com/security/cve/CVE-2026-4740 Types: Vendor Advisory
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      Reference typeremoved
      https://blog.arfevrier.fr/open-cluster-management-cross-cluster-escape/ Types: Exploit, Third Party Advisory
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      Reference typeremoved
      https://bugzilla.redhat.com/show_bug.cgi?id=2450590 Types: Issue Tracking, Vendor Advisory
      —

      Source identifier: secalert@redhat.com

    Show 14 older changes

    1. Record modifiedRed Hat ADP

      Show 18 original changes
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Referenceadded
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      https://access.redhat.com/errata/RHSA-2026:11414
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      https://access.redhat.com/errata/RHSA-2026:13542
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      https://access.redhat.com/errata/RHSA-2026:13853
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      https://access.redhat.com/errata/RHSA-2026:8218
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      https://access.redhat.com/errata/RHSA-2026:9848
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      https://access.redhat.com/security/cve/CVE-2026-4740
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      https://bugzilla.redhat.com/show_bug.cgi?id=2450590
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      https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-4740.json
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      https://access.redhat.com/errata/RHSA-2026:11414
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      https://access.redhat.com/errata/RHSA-2026:13542
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      https://access.redhat.com/errata/RHSA-2026:13853
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      https://access.redhat.com/errata/RHSA-2026:8218
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      https://access.redhat.com/errata/RHSA-2026:9848
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      https://access.redhat.com/security/cve/CVE-2026-4740
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      https://bugzilla.redhat.com/show_bug.cgi?id=2450590
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      https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-4740.json
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      Reference typeremoved
      https://access.redhat.com/security/cve/CVE-2026-4740 Types: Vendor Advisory
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      Reference typeremoved
      https://bugzilla.redhat.com/show_bug.cgi?id=2450590 Types: Issue Tracking, Vendor Advisory
      —

      Source identifier: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c

    2. Record modifiedRed Hat ADP

      1 individual change: Affected versions (publisher)

      Show the original change
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Affected versions (publisher)changed
      multicluster engine for Kubernetes 2.1, multicluster engine for Kubernetes 2.11, multicluster engine for Kubernetes 2.6 (+8)
      multicluster engine for Kubernetes 2.10, multicluster engine for Kubernetes 2.11.0, multicluster engine for Kubernetes 2.6 (+8)

      Source identifier: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c

    3. Record modifiedRed Hat

      1 individual change: Affected versions (publisher)

      Show the original change
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Affected versions (publisher)changed
      multicluster engine for Kubernetes 2.10, multicluster engine for Kubernetes 2.11, multicluster engine for Kubernetes 2.6 (+8)
      multicluster engine for Kubernetes 2.10, multicluster engine for Kubernetes 2.11.0, multicluster engine for Kubernetes 2.6 (+8)

      Source identifier: secalert@redhat.com

    4. Record modifiedRed Hat

      1 individual change: Affected versions (publisher)

      Show the original change
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Affected versions (publisher)changed
      multicluster engine for Kubernetes 2.1, multicluster engine for Kubernetes 2.11, multicluster engine for Kubernetes 2.6 (+8)
      multicluster engine for Kubernetes 2.10, multicluster engine for Kubernetes 2.11, multicluster engine for Kubernetes 2.6 (+8)

      Source identifier: secalert@redhat.com

    5. Record modifiedRed Hat ADP

      1 individual change: Affected versions (publisher)

      Show the original change
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Affected versions (publisher)changed
      multicluster engine for Kubernetes 2.10, multicluster engine for Kubernetes 2.11, multicluster engine for Kubernetes 2.6 (+8)
      multicluster engine for Kubernetes 2.1, multicluster engine for Kubernetes 2.11, multicluster engine for Kubernetes 2.6 (+8)

      Source identifier: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c

    6. Record modifiedRed Hat

      1 individual change: Affected versions (publisher)

      Show the original change
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Affected versions (publisher)changed
      multicluster engine for Kubernetes 2.1, multicluster engine for Kubernetes 2.11, multicluster engine for Kubernetes 2.6 (+8)
      multicluster engine for Kubernetes 2.1, multicluster engine for Kubernetes 2.11, multicluster engine for Kubernetes 2.6 (+8)

      Source identifier: secalert@redhat.com

    7. Record modifiedRed Hat ADP

      1 individual change: Affected versions (publisher)

      Show the original change
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Affected versions (publisher)changed
      multicluster engine for Kubernetes 2.1, multicluster engine for Kubernetes 2.11, multicluster engine for Kubernetes 2.6 (+8)
      multicluster engine for Kubernetes 2.10, multicluster engine for Kubernetes 2.11, multicluster engine for Kubernetes 2.6 (+8)

      Source identifier: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c

    8. Record modifiedRed Hat

      1 individual change: Affected versions (publisher)

      Show the original change
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Affected versions (publisher)changed
      multicluster engine for Kubernetes 2.1, multicluster engine for Kubernetes 2.11, multicluster engine for Kubernetes 2.6 (+8)
      multicluster engine for Kubernetes 2.10, multicluster engine for Kubernetes 2.11, multicluster engine for Kubernetes 2.6 (+8)

      Source identifier: secalert@redhat.com

    9. Record modifiedRed Hat

      1 individual change: Affected versions (publisher)

      Show the original change
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Affected versions (publisher)changed
      multicluster engine for Kubernetes 2.10, multicluster engine for Kubernetes 2.11, multicluster engine for Kubernetes 2.6 (+8)
      multicluster engine for Kubernetes 2.1, multicluster engine for Kubernetes 2.11, multicluster engine for Kubernetes 2.6 (+8)

      Source identifier: secalert@redhat.com

    10. Record modifiedRed Hat

      1 individual change: Affected versions (publisher)

      Show the original change
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Affected versions (publisher)changed
      multicluster engine for Kubernetes 2.1, multicluster engine for Kubernetes 2.11, multicluster engine for Kubernetes 2.6 (+8)
      multicluster engine for Kubernetes 2.10, multicluster engine for Kubernetes 2.11, multicluster engine for Kubernetes 2.6 (+8)

      Source identifier: secalert@redhat.com

    11. Record modifiedRed Hat ADP

      1 individual change: Affected versions (publisher)

      Show the original change
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Affected versions (publisher)changed
      multicluster engine for Kubernetes 2.1, multicluster engine for Kubernetes 2.11, multicluster engine for Kubernetes 2.6 (+8)
      multicluster engine for Kubernetes 2.1, multicluster engine for Kubernetes 2.11, multicluster engine for Kubernetes 2.6 (+8)

      Source identifier: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c

    12. Record modifiedRed Hat

      1 individual change: Affected versions (publisher)

      Show the original change
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Affected versions (publisher)changed
      multicluster engine for Kubernetes 2.1, multicluster engine for Kubernetes 2.11, multicluster engine for Kubernetes 2.6 (+8)
      multicluster engine for Kubernetes 2.1, multicluster engine for Kubernetes 2.11, multicluster engine for Kubernetes 2.6 (+8)

      Source identifier: secalert@redhat.com

    13. Record modifiedRed Hat

      1 individual change: Affected versions (publisher)

      Show the original change
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Affected versions (publisher)changed
      multicluster engine for Kubernetes 2.1, multicluster engine for Kubernetes 2.11.0, multicluster engine for Kubernetes 2.6 (+8)
      multicluster engine for Kubernetes 2.1, multicluster engine for Kubernetes 2.11, multicluster engine for Kubernetes 2.6 (+8)

      Source identifier: secalert@redhat.com

    14. Record modifiedRed Hat

      Show 4 original changes
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Referenceadded
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      https://access.redhat.com/errata/RHSA-2026:11414
      Referenceadded
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      https://access.redhat.com/errata/RHSA-2026:13853
      Referenceadded
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      https://access.redhat.com/errata/RHSA-2026:9848
      Affected versions (publisher)changed
      Multicluster Engine for Kubernetes, Multicluster Engine for Kubernetes, Multicluster Engine for Kubernetes (+4)
      multicluster engine for Kubernetes 2.11, multicluster engine for Kubernetes 2.6, multicluster engine for Kubernetes 2.9 (+6)

      Source identifier: secalert@redhat.com

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    Badge preview for CVE-2026-4740
    <a href="https://intel.neosec.eu/en/cve/CVE-2026-4740"><img src="https://intel.neosec.eu/badge/cve/CVE-2026-4740.svg?lang=en" alt="CVE-2026-4740 – NEOSEC Intel" height="20"></a>