CVE-2026-42266 JupyterLab has an Extension Manager API/GUI Policy Discrepancy, allowing 3rd party (malicious) extensions install via POST request
Attackers can bypass extension allow-lists to install malicious third-party extensions via POST requests, leading to potential code execution.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-42266?
CVE-2026-42266 is a high-severity vulnerability in jupyterlab, published on 13 May 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Official 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.
Which versions are affected by CVE-2026-42266?
4 open source packages ship an affected version, including jupyterlab. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
jupyterlab Bitnami | From 4.0.0 | 4.5.7 |
jupyterlab PyPI | From 4.0.0 | 4.5.7 |
jupyterlab PyPI | From 4.0.0 | 4.5.7 |
jupyterlab PyPI | From 4.0.0 | 4.5.7 |
Products include Jupyter Jupyterlab.
How do I fix CVE-2026-42266?
Upgrade jupyterlab to 4.5.7 or later.
Is CVE-2026-42266 being exploited?
There is no known exploitation of CVE-2026-42266 in the wild and no public exploit code.
Other vulnerabilities in jupyterlab
- CVE-2024-39700 Remote Code Execution (RCE) vulnerability in jupyterlab extension template `update-integration-tests` GitHub Action
- CVE-2026-42557 jupyterlab: Command linker attributes in HTML enable one-click command execution from untrusted content
- CVE-2024-43805 HTML injection in Jupyter Notebook and JupyterLab leading to DOM Clobbering
- CVE-2021-32797 JupyterLab: XSS due to lack of sanitization of the action attribute of an html <form>
- CVE-2025-59842 JupyterLab LaTeX typesetter links did not enforce `noopener` attribute
Sources
Also known as BIT-jupyterlab-2026-42266, CLEANSTART-2026-KE39444, CLEANSTART-2026-PS25216, DEBIAN-CVE-2026-42266, GHSA-37w4-hwhx-4rc4, PYSEC-2026-164 and 1 more.