CVE-2026-42266highCWE-602CWE-88

CVE-2026-42266: high-severity vulnerability in jupyterlab

JupyterLab has an Extension Manager API/GUI Policy Discrepancy allowing 3rd party (malicious) extensions install via POST request.

Published · Updated

21Vexday Risk Score

No sign of exploitation. No public exploitation artifact known so far.

ssvc Trackcvss 8.8epss 0.9%
exploitation probability
0.9%top 43% of all CVEs
observed exploitation
nono source reports it
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.
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Affected products
jupyterlab · jupyterlab
Related CVEs — jupyterlab

In the same product, most dangerous first.

CVE-2021-32797HIGHJupyterLab: XSS due to lack of sanitization of the action attribute of an html <form>EPSS 2.7%CVE-2026-73417HIGHJupyterLab: Cross-site scripting (XSS) via crafted settings file (`overrides.json`)EPSS 0.7%CVE-2026-73415HIGHjupyterlab: Image viewer in JupyterLab allows XSS when opening malicious image in new browser tabEPSS 0.7%CVE-2026-42557HIGHjupyterlab: Command linker attributes in HTML enable one-click command execution from untrusted contentEPSS 0.7%CVE-2024-22421HIGHPotential authentication and CSRF tokens leak in JupyterLabEPSS 0.7%CVE-2026-73416MEDIUMjupyterlab: PyPI extension blocklist package-name canonicalization bypassEPSS 0.7%
References
https://access.redhat.com/errata/RHSA-2026:43038https://access.redhat.com/errata/RHSA-2026:60520https://access.redhat.com/security/cve/CVE-2026-42266https://bugzilla.redhat.com/show_bug.cgi?id=2477072https://github.com/jupyterlab/jupyterlab/releases/tag/v4.5.7https://github.com/jupyterlab/jupyterlab/security/advisories/GHSA-37w4-hwhx-4rc4https://jupyterhub.readthedocs.io/en/5.2.1/explanation/websecurity.htmlhttps://jupyterlab.readthedocs.io/en/latest/user/extensions.html#extension-manager-implementationshttps://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-42266.json