CVE-2026-42266: JupyterLab has an Extension Manager API/GUI Policy Discrepancy, allowing 3rd party (malicious) extensions install via POST request
(updated )
The allow-list of extensions that can be installed from PyPI Extension Manager (allowed_extensions_uris) is not correctly enforced by JupyterLab prior to 4.5.7. The PyPI Extension Manager was not contained to packages listed on the default PyPI index.
This has security implications for deployments that:
- have allow-listed specific extensions with aim to prevent users from installing packages
- have the kernel and terminals disabled or delegated to remote hosts (thus no access to install packages in the single-user server environment)
- have multi-tenant deployments that is not configured for untrusted users (as per documented on JupyterHub https://jupyterhub.readthedocs.io/en/5.2.1/explanation/websecurity.html)
- have the (default) PyPI Extension Manager enabled
References
- github.com/advisories/GHSA-37w4-hwhx-4rc4
- github.com/jupyterlab/jupyterlab/releases/tag/v4.5.7
- github.com/jupyterlab/jupyterlab/security/advisories/GHSA-37w4-hwhx-4rc4
- github.com/pypa/advisory-database/tree/main/vulns/jupyterlab/PYSEC-2026-164.yaml
- jupyterhub.readthedocs.io/en/5.2.1/explanation/websecurity.html
- jupyterlab.readthedocs.io/en/latest/user/extensions.html
- nvd.nist.gov/vuln/detail/CVE-2026-42266
Code Behaviors & Features
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