Jupyter: JupyterLab's command linker attributes in HTML enable one-click command execution from untrusted…
Jupyter
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- Severity
- Critical, CVSS 9.6
- CVSS vector
- CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:H
- Record
- CVE-2026-42557
- Affects
- Jupyter
- Known exploited
- Not listed in the CISA Known Exploited Vulnerabilities catalog
- Published
- Record first published by the source
- May 13, 2026
- Source last modified
- October 25, 2026
Description
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.
Description quoted from the NVD record.
Who is affected
Jupyter (also called JupyterLab) is a tool for writing and running computer code alongside notes and results in documents called notebooks. This flaw affects versions before 4.5.7. The part of the product that cleans up web page content shown inside notebooks lets through buttons that can trigger JupyterLab commands. A notebook with a misleading button saved in its results could, with a single click on that button, run any JupyterLab command, including running code of an attacker's choosing, even though the user never chose to run any code. This flaw is rated Critical.
What to do
- The person who installed or runs Jupyter for your organization should handle this, or the IT provider or vendor who manages it for you.
- Update JupyterLab (the
jupyterlabpackage) to version4.5.7, which fixes this flaw. Any version before 4.5.7 is affected. - Check each computer or server where your organization uses Jupyter, so that none is left on an affected version.
- If an IT provider or vendor runs Jupyter for your organization, send them this advisory and ask when the update to
4.5.7will be done.
Analysis written from the source record as of October 25, 2026 and reviewed before publishing.