Jupyter: JupyterLab has an Extension Manager API/GUI Policy Discrepancy, allowing 3rd party (malicious)…
Jupyter
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- Severity
- High, CVSS 8.8
- CVSS vector
- CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
- Record
- CVE-2026-42266
- 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
- August 28, 2026
Description
JupyterLab is an extensible environment for interactive and reproducible computing, based on the Jupyter Notebook Architecture. From 4.0.0 to 4.5.6, the allow-list of extensions that can be installed from PyPI Extension Manager (allowed_extensions_uris) is not correctly enforced by JupyterLab. The PyPI Extension Manager was not contained to packages listed on the default PyPI index. This vulnerability is fixed in 4.5.7.
Description quoted from the NVD record.
Who is affected
This flaw affects Jupyter (also called JupyterLab), a program where people write and run code alongside notes and charts in shared documents called notebooks. It affects versions 4.0.0 through 4.5.6. The problem is in the Extension Manager, the part of the program used to find and install add-ons. If your organization uses an approved list to limit which add-ons can be installed, that list is not properly enforced, and installs are not kept to the standard public add-on catalog. As a result, someone could install add-ons, including possibly harmful ones from third parties, that your list was meant to block. This flaw is rated High.
What to do
- The person who installed or looks after JupyterLab at your organization should act on this. If an IT provider or vendor runs it for you, send them this advisory and ask when the update will be done.
- Update JupyterLab to version
4.5.7or later, which fixes this flaw. - If your organization runs more than one copy of JupyterLab, for example on several computers or a shared server, update every copy on a version from 4.0.0 through 4.5.6.
- After updating, check which add-ons are installed and remove any that your organization did not approve.
Analysis written from the source record as of August 28, 2026 and reviewed before publishing.