HighCVE-2026-42266

    Jupyterlab: Argument Injection (CVE-2026-42266)

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

    What is affected, what to do

    A flaw was found in JupyterLab, an extensible environment for interactive computing. The PyPI Extension Manager, responsible for installing extensions, failed to properly enforce its allow-list of approved extensions.

    Update jupyterlab to version 4.5.7.

    Affected
    • Jupyterlab gte 4.0.0, < 4.5.7..*

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

    Metrics

    8.8

    Priority

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

    Source: NVD, CVSS v3

    8.8

    CVSS v3

    Severity High on the scale from 0 to 10.

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

    5.7 %

    EPSS score

    Moderate — model estimates 1-10% exploitation likelihood.

    Source: FIRST EPSS, percentile 93.0

    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
    130.49 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
    8.8 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
    8.8
    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
    5.7 %
    Moderate — model estimates 1-10% 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
    93.0
    Critical — this CVE ranks in the top fifth of all CVEs scored today (rank ≥ 80%).
    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
    CISA assessment (SSVC)
    Exploitation: none known · not automatable · Technical impact: total
    Source: CISA Vulnrichment, as of 13 May 2026
    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-88, CWE-602

    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 JupyterLab, an extensible environment for interactive computing. The PyPI Extension Manager, responsible for installing extensions, failed to properly enforce its allow-list of approved extensions. This vulnerability allowed for the installation of unauthorized extensions from sources outside the default PyPI index. Exploitation of this flaw could lead to arbitrary code execution and significant system compromise.

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

    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
    jupyterlabjupyterlab
    • ≥ 4.0.0, < 4.5.7
    • —
    jupyterjupyterlab
    • 4.0.0 – < 4.5.7
    • 4.5.7
    pypijupyterlab
    • 4.1.3
    • 4.2.0b1
    • 4.4.0a3
    • 4.5.2
    • 4.0.0
    • 4.0.8
    • 4.5.0
    • 4.3.0b0
    • 4.1.1
    • 4.1.0b1
    • 4.2.3
    • 4.5.0a3
    • 4.4.0
    • 4.3.1
    • 4.4.0a2
    • 4.5.0b0
    • 4.4.1
    • 4.0.12
    • 4.2.6
    • 4.1.0b2
    • 4.4.0a0
    • 4.4.0b1
    • 4.5.0rc0
    • 4.0.5
    • 4.5.0a2
    • 4.4.5
    • 4.0.3
    • 4.3.0b2
    • 4.2.0b3
    • 4.2.7
    • 4.5.0a4
    • 4.2.0
    • 4.4.3
    • 4.1.0rc0
    • 4.4.0b2
    • 4.3.0b1
    • 4.0.7
    • 4.1.4
    • 4.3.0a2
    • 4.3.5
    • 4.0.6
    • 4.4.0rc1
    • 4.3.0a0
    • 4.1.5
    • 4.5.1
    • 4.5.3
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    Vendors and products

    Weakness classes (CWE)

    • CWE-88Improper Neutralization of Argument Delimiters in a Command ('Argument Injection')

      Base

      The product constructs a string for a command to be executed by a separate component in another control sphere, but it does not properly delimit the intended arguments, options, or switches within that command string.

      Entry at MITRE CWE-88

    • CWE-602Client-Side Enforcement of Server-Side Security

      Class

      The product is composed of a server that relies on the client to implement a mechanism that is intended to protect the server.

      Entry at MITRE CWE-602

    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 modifiedGitHub

      Show 12 original changes
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Referenceadded
      —
      https://github.com/jupyterlab/jupyterlab/releases/tag/v4.5.7
      Referenceadded
      —
      https://github.com/jupyterlab/jupyterlab/security/advisories/GHSA-37w4-hwhx-4rc4
      Referenceadded
      —
      https://jupyterhub.readthedocs.io/en/5.2.1/explanation/websecurity.html
      Referenceadded
      —
      https://jupyterlab.readthedocs.io/en/latest/user/extensions.html#extension-manager-implementations
      Referenceremoved
      https://github.com/jupyterlab/jupyterlab/releases/tag/v4.5.7
      —
      Referenceremoved
      https://github.com/jupyterlab/jupyterlab/security/advisories/GHSA-37w4-hwhx-4rc4
      —
      Referenceremoved
      https://jupyterhub.readthedocs.io/en/5.2.1/explanation/websecurity.html
      —
      Referenceremoved
      https://jupyterlab.readthedocs.io/en/latest/user/extensions.html#extension-manager-implementations
      —
      Reference typeremoved
      https://github.com/jupyterlab/jupyterlab/releases/tag/v4.5.7 Types: Patch, Release Notes
      —
      Reference typeremoved
      https://github.com/jupyterlab/jupyterlab/security/advisories/GHSA-37w4-hwhx-4rc4 Types: Mitigation, Vendor Advisory
      —
      Reference typeremoved
      https://jupyterhub.readthedocs.io/en/5.2.1/explanation/websecurity.html Types: Product
      —
      Reference typeremoved
      https://jupyterlab.readthedocs.io/en/latest/user/extensions.html#extension-manager-implementations Types: Product
      —

      Source identifier: security-advisories@github.com

    2. Record modifiedRed Hat ADP

      Show 10 original changes
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Affected versions (publisher)added
      —
      Affected value modified. <a href="https://github.com/CVEProject/cvelistV5/blob/main/cves/2026/42xxx/CVE-2026-42266.json">CVE-2026-42266</a>
      Referenceadded
      —
      https://access.redhat.com/errata/RHSA-2026:43038
      Referenceadded
      —
      https://access.redhat.com/errata/RHSA-2026:60520
      Referenceadded
      —
      https://access.redhat.com/security/cve/CVE-2026-42266
      Referenceadded
      —
      https://bugzilla.redhat.com/show_bug.cgi?id=2477072
      Referenceadded
      —
      https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-42266.json
      Referenceremoved
      https://access.redhat.com/errata/RHSA-2026:43038
      —
      Referenceremoved
      https://access.redhat.com/security/cve/CVE-2026-42266
      —
      Referenceremoved
      https://bugzilla.redhat.com/show_bug.cgi?id=2477072
      —
      Referenceremoved
      https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-42266.json
      —

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

    3. Record modifiedRed Hat ADP

      Show 2 original changes
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Referenceadded
      —
      https://access.redhat.com/errata/RHSA-2026:43038
      Affected versions (publisher)changed
      Migration Toolkit for Applications 8, Red Hat OpenShift AI (RHOAI), Red Hat OpenShift AI (RHOAI) (+13)
      Red Hat Migration Toolkit for Applications 8.2, Red Hat OpenShift AI (RHOAI), Red Hat OpenShift AI (RHOAI) (+13)

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

    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)changed
      Migration Toolkit for Applications 8, Red Hat OpenShift AI (RHOAI)
      Migration Toolkit for Applications 8, Red Hat OpenShift AI (RHOAI)

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

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