What’s Vulnerable › Vulnerabilities

CVE-2026-42266: JupyterLab has an Extension Manager API/GUI Policy Discrepancy allowing 3rd party (malicious) extensions install via POST request.

• Severity: high (CVSS 8.8 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 5.7% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-05-13 · updated 2026-08-28
• Weakness: CWE-88

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.

Affected products

• jupyterlab: from 4.0.0 before 4.5.7 — fixed in 4.5.7

How to fix

Upgrade to a fixed version: jupyterlab 4.5.7. Check the vendor advisory for mitigations.

References

• https://github.com/jupyterlab/jupyterlab/releases/tag/v4.5.7
• https://github.com/jupyterlab/jupyterlab/security/advisories/GHSA-37w4-hwhx-4rc4
• https://jupyterhub.readthedocs.io/en/5.2.1/explanation/websecurity.html
• https://jupyterlab.readthedocs.io/en/latest/user/extensions.html#extension-manager-implementations
• https://access.redhat.com/errata/RHSA-2026:43038
• https://access.redhat.com/errata/RHSA-2026:60520
• https://access.redhat.com/security/cve/CVE-2026-42266
• https://bugzilla.redhat.com/show_bug.cgi?id=2477072
• https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-42266.json

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