JupyterLab has an Extension Manager API/GUI Policy Discrepancy, allowing 3rd party (malicious) extensions install via POST request
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
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=readonlyor the following traitlet:
c.LabApp.extension_manager = 'readonly'You can confirm that the read-only manager is in use from GUI:
<img width="293" height="293" alt="image" src="https://github.com/user-attachments/assets/8016c809-633e-4ed0-a5bc-6bc4793caa0f" />Note: configuration of a PyPI proxy with allow-listed packages is not sufficient to protect from this vulnerability.
References
Affected software
Click a technology to see all vulnerabilities affecting it.
| Platform | Package | Vulnerable versions | Fixed in |
|---|---|---|---|
| Python (PyPI) | jupyterlab | >= 4.0.0, < 4.5.7 | 4.5.7 |
References
- https://jupyterhub.readthedocs.io/en/5.2.1/explanation/websecurity.html
- https://jupyterlab.readthedocs.io/en/latest/user/extensions.html#extension-manager-implementations
- https://github.com/jupyterlab/jupyterlab/security/advisories/GHSA-37w4-hwhx-4rc4
- https://github.com/jupyterlab/jupyterlab/releases/tag/v4.5.7
- https://nvd.nist.gov/vuln/detail/CVE-2026-42266
- https://github.com/jupyterlab/jupyterlab
- https://github.com/pypa/advisory-database/tree/main/vulns/jupyterlab/PYSEC-2026-164.yaml
- CVSS vector
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H- Weakness (CWE)
CWE-20, CWE-602, CWE-88- Platform
- Python (PyPI)
- Package
jupyterlab- Disclosed
- 05.05.2026
- Updated
- 11.10.2026 15:17
Sources and licenses
OSV / GitHub Advisory Database - PYSEC-2026-164 - PyPA Advisory Database; CC BY 4.0
OSV / GitHub Advisory Database - GHSA-37w4-hwhx-4rc4 - CC BY 4.0
Vulnerability history: jupyterlab
All published vulnerabilities of this package (Python (PyPI)), newest first. Shows whether this is a one-off slip or a package that needs watching.
- Total entries
- 19
- First → latest
- 08.2021 10.2026
- Without a fix
- 0
- Exploited in attacks
- 0
Severity breakdown
- Critical 1
- High 8
- Medium 8
- Low 2
Disclosures per year
- 2021: 1
- 2022: 0
- 2023: 0
- 2024: 4
- 2025: 1
- 2026: 13
-
JupyterLab has an Extension Manager API/GUI Policy Discrepancy, allowing 3rd party (malicious) extensions install via POST request this entry
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