PT-2026-37256 · Pypi · Jupyterlab

Published 2026-05-05 · Updated 2026-05-05 · CVE-2026-42266

OSV

CVSS v3.1

8.8

High

Base vector

AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

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.X. 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 Manger enabled

Impact

An authenticated attacker - such as a student in a shared JupyterHub environment or a user in a multi-tenant JupyterLab deployment - can escalate their privileges. This might allow for data exfiltration, lateral movement within the network, and persistent compromise of the server infrastructure.

Patches

JupyterLab v4.5.7 contains the patch.

Users of applications that depend on JupyterLab, such as Notebook v7+, should update jupyterlab package too.

Workarounds

Switch to read-only extension manager by adding the following command line option:

--LabApp.extension manager=readonly

or the following traitlet:

c.LabApp.extension manager = 'readonly'

You can confirm that the read-only manager is in use from GUI:

Note: configuration of a PyPI proxy with allow-listed packages is not sufficient to protect from this vulnerability.

Resources

• allow-list https://jupyterlab.readthedocs.io/en/stable/user/extensions.html#listing-configuration
• https://jupyterhub.readthedocs.io/en/5.2.1/explanation/websecurity.html
• https://jupyterlab.readthedocs.io/en/latest/user/extensions.html#extension-manager-implementations

Fix

Argument Injection

RCE

Weakness Enumeration

CWE-602

CWE-88

CWE-20

Related Identifiers

CVE-2026-42266

GHSA-37W4-HWHX-4RC4

Affected Products

Jupyterlab

References · 6

• https://osv.dev/vulnerability/GHSA-37w4-hwhx-4rc4 · Vendor Advisory
• https://github.com/jupyterlab/jupyterlab · Note
• https://github.com/jupyterlab/jupyterlab/releases/tag/v4.5.7 · Note
• https://jupyterhub.readthedocs.io/en/5.2.1/explanation/websecurity.html · Note
• https://github.com/jupyterlab/jupyterlab/security/advisories/GHSA-37w4-hwhx-4rc4 · Note
• https://jupyterlab.readthedocs.io/en/latest/user/extensions.html#extension-manager-implementations · Note