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JupyterlabApplication · Jupyter

CVE-2026-42557

CRITICAL · 9.6 CVSS v3.1 Published 2026-05-13
Fix available
A fix is available. Upgrade to 4.5.7 / 7.5.6 or later.
See remediation →
100/100
Remediation priority · Urgent
Remotely reachable No privileges

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
jupyterlab is an extensible environment for interactive and reproducible computing, based on the Jupyter Notebook Architecture. Prior to 4.5.7, JupyterLab's HTML sanitizer allowlists data-commandlinker-command and data-commandlinker-args on button elements, while CommandLinker listens for all click events on document.body and executes the named command without checking whether the element came from trusted JupyterLab UI. A notebook with a pre-saved HTML cell output containing a deceptive button can trigger arbitrary JupyterLab commands - including arbitrary code execution - on a single user click, without any code being submitted for execution by the user. This vulnerability is fixed in 4.5.7.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

JupyterLab's HTML sanitizer prior to 4.5.7 allowlisted data-commandlinker-command and data-commandlinker-args attributes on button elements. The CommandLinker component listens for click events on document.body and executes commands without validating the element originated from trusted JupyterLab UI, allowing a malicious HTML cell output to trigger arbitrary code execution via a single click.

MitigationUpgrade JupyterLab to version 4.5.7 or later, which contains the fix to remove the unsafe attributes from the HTML sanitizer allowlist.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
JupyterlabApplication
Affected:< 4.5.7
NotebookApplication
Affected:>= 7.0.0, < 7.5.6

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
Required
Scope
Changed
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:H

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Identify which Jupyter product is running
    Run 'jupyter --version' or check the application name in the browser title bar (JupyterLab or Notebook 7.x)
    Affected if Product is JupyterLab or Jupyter Notebook 7.x
  2. Determine installed JupyterLab version
    Run 'jupyter lab --version' or check the package.json in the jupyterlab environment: pip show jupyterlab
    Affected if Version is lower than 4.5.7 (e.g., 4.5.6, 4.4.x, etc.)
  3. Determine installed Jupyter Notebook version
    Run 'jupyter notebook --version' or check the package.json: pip show notebook
    Affected if Version is 7.0.0 through 7.5.5 (>= 7.0.0 and < 7.5.6)
  4. Confirm HTML output capability is enabled
    Check if notebooks can execute code and display HTML output - this is enabled by default in JupyterLab and Notebook 7.x
    Affected if HTML cell outputs can be rendered (default behavior in affected versions)

You are affected if running JupyterLab version < 4.5.7 or Jupyter Notebook version >= 7.0.0 and < 7.5.6, and users have the ability to render HTML in notebook cell outputs (default enabled).

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to 4.5.7 / 7.5.6 or later
Fixed in 4.5.77.5.6
Interim mitigation

Upgrade JupyterLab to version 4.5.7 or later, which contains the fix to remove the unsafe attributes from the HTML sanitizer allowlist.

Recommended fix High confidence

jupyterlab >= 4.5.7 | notebook >= 7.5.6

  1. Upgrade JupyterLab to version 4.5.7 or later by running: pip install --upgrade jupyterlab
  2. Alternatively or additionally, upgrade Notebook to version 7.5.6 or later by running: pip install --upgrade notebook
  3. Restart the Jupyter server after upgrading to ensure the new version is loaded
  4. Verify the upgrade was successful by checking the installed version: pip show jupyterlab (or pip show notebook)

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Jupyterlab Scoped from the published advisory
  • Consultation2.0 h
  • Implementation3.0 h
  • Testing3.0 h
  • Review / QA2.0 h
10.0 hours of engineering $1,750
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $2,800.

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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2026-42557 in production — separate from our analysis above.

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data