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CVE-2026-42266

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

8.8 HighFix available

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.

Attack profile

How easy it is to exploit

Attack vector
Network
Complexity
Low
Privileges needed
Low
User interaction
None

What an attacker can affect

Confidentiality
High
Integrity
High
Availability
High

Exploit likelihood

5.65%Up 5.6 points since May 14, 2026
90%50%10%1%

What each source reports

CVE List Score used 8.8

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

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.

Record
CVE-2026-42266
CVSS 3.1
8.8 HighCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Weakness
CWE-88, CWE-602, CWE-88
Updated
2026-11-02
EUVDEUVD-2026-29995 8.8

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.

Record
EUVD-2026-29995
CVSS 3.1
8.8 HighCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Updated
2026-11-02
GitHub AdvisoriesGHSA-37w4-hwhx-4rc4 8.8

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=readonly

or 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

Record
GHSA-37w4-hwhx-4rc4
CVSS 3.1
8.8 HighCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Weakness
CWE-20, CWE-88, CWE-602
Updated
2026-11-02
NVD 8.8

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.

Record
CVE-2026-42266
CVSS 3.1
8.8 HighCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Weakness
CWE-88, CWE-602
Updated
2026-11-02
OSV 8.8

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

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.

Record
CVE-2026-42266
CVSS 3.1
8.8 HighCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Weakness
CWE-602, CWE-88
Updated
2026-11-06
OSVDEBIAN-CVE-2026-42266 8.8

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.

Record
DEBIAN-CVE-2026-42266
CVSS 3.1
8.8 HighCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Updated
2026-11-02
Show 5 moreShow less
OSVGHSA-37w4-hwhx-4rc4 8.8

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=readonly

or 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

Record
GHSA-37w4-hwhx-4rc4
CVSS 3.1
8.8 HighCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Weakness
CWE-20, CWE-602, CWE-88
Updated
2026-11-02
OSVPYSEC-2026-164 8.8

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.

Record
PYSEC-2026-164
CVSS 3.1
8.8 HighCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Updated
2026-11-02
OSVUBUNTU-CVE-2026-42266 8.8

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.

Record
UBUNTU-CVE-2026-42266
CVSS 3.1
8.8 HighCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Updated
2026-11-02
OSVBIT-jupyterlab-2026-42266 No score

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

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.

Record
BIT-jupyterlab-2026-42266
Updated
2026-11-02
OSVopenSUSE-SU-2026:10748-1 No score

jupyter-jupyterlab-4.5.7-1.1 on GA media

These are all security issues fixed in the jupyter-jupyterlab-4.5.7-1.1 package on the GA media of openSUSE Tumbleweed.

Record
openSUSE-SU-2026:10748-1
Updated
2026-11-02

Affected products

Affected packages

Affected packages
PackageAffectedFixed
jupyterlab
PyPI
 4.0.0 to 4.5.6
4.5.7
jupyterlab
Bitnami
 4.0.0 up to 4.5.7
4.5.7
jupyterlab
Debian:13
 All versions, plus listed versions
4.0.11+ds1+~cs11.25.27-74.0.11+ds1+~cs11.25.27-84.0.11+ds1+~cs11.25.27-94.0.11+ds2+~cs11.25.27-14.0.11+ds2+~cs11.25.27-3
Show 24 moreShow less
4.0.11+ds3+~cs11.25.27-14.0.11+ds4+~cs11.25.27-14.0.11+ds4+~cs11.25.27-24.0.11+ds4+~cs11.25.27-34.0.11+ds4+~cs11.25.27-44.0.11+ds5+~cs11.25.27-14.0.13+ds1+~2.0.1+~cs1.4.4-14.1.3+ds1+~2.0.1+~0.15.3+~cs1.4.4-14.1.8+ds1+~2.0.1+~0.15.3+~cs1.4.4-14.1.8+ds1+~2.0.1+~0.15.3+~cs1.4.4-24.1.8+ds1+~2.0.1+~0.15.3+~cs1.4.4-34.1.8+ds1+~2.0.1+~0.15.3+~cs1.4.4-44.1.8+ds1+~2.0.1+~0.15.3+~cs1.4.4-54.1.8+ds1+~2.0.1+~0.15.3+~cs1.4.4-64.1.8+ds1+~2.0.1+~0.15.3+~cs1.4.4-74.1.8+ds1+~2.0.1+~0.15.3+~cs1.4.4-84.4.1+ds1+~3.0.5+~0.16.6+~cs1.4.4-14.4.10+ds1+~3.1.0+~0.16.6+~cs1.4.4-14.4.10+ds1+~3.1.0+~0.16.6+~cs1.4.4-24.4.10+ds1+~3.1.0+~0.16.6+~cs1.4.4-34.4.10+ds1+~3.1.0+~0.16.6+~cs1.4.4-44.4.10+ds1+~3.1.0+~0.16.6+~cs1.4.4-54.4.10+ds1+~3.1.0+~0.16.6+~cs1.4.4-64.4.8+ds1+~3.1.0+~0.16.6+~cs1.4.4-1
 None known
jupyterlab
Debian:14
 before 4.4.10+ds1+~3.1.0+~0.16.6+~cs1.4.4-3, plus listed versions
4.0.11+ds1+~cs11.25.27-74.0.11+ds1+~cs11.25.27-84.0.11+ds1+~cs11.25.27-94.0.11+ds2+~cs11.25.27-14.0.11+ds2+~cs11.25.27-3
Show 20 moreShow less
4.0.11+ds3+~cs11.25.27-14.0.11+ds4+~cs11.25.27-14.0.11+ds4+~cs11.25.27-24.0.11+ds4+~cs11.25.27-34.0.11+ds4+~cs11.25.27-44.0.11+ds5+~cs11.25.27-14.0.13+ds1+~2.0.1+~cs1.4.4-14.1.3+ds1+~2.0.1+~0.15.3+~cs1.4.4-14.1.8+ds1+~2.0.1+~0.15.3+~cs1.4.4-14.1.8+ds1+~2.0.1+~0.15.3+~cs1.4.4-24.1.8+ds1+~2.0.1+~0.15.3+~cs1.4.4-34.1.8+ds1+~2.0.1+~0.15.3+~cs1.4.4-44.1.8+ds1+~2.0.1+~0.15.3+~cs1.4.4-54.1.8+ds1+~2.0.1+~0.15.3+~cs1.4.4-64.1.8+ds1+~2.0.1+~0.15.3+~cs1.4.4-74.1.8+ds1+~2.0.1+~0.15.3+~cs1.4.4-84.4.1+ds1+~3.0.5+~0.16.6+~cs1.4.4-14.4.10+ds1+~3.1.0+~0.16.6+~cs1.4.4-14.4.10+ds1+~3.1.0+~0.16.6+~cs1.4.4-24.4.8+ds1+~3.1.0+~0.16.6+~cs1.4.4-1
4.4.10+ds1+~3.1.0+~0.16.6+~cs1.4.4-3
jupyterlab
PyPI
 4.0.0 up to 4.5.7, plus listed versions
4.0.14.0.104.0.114.0.124.0.13
Show 45 moreShow less
4.0.24.0.34.0.44.0.54.0.64.0.74.0.84.0.94.1.04.1.0a14.1.0a24.1.0a34.1.0a44.1.0b04.1.0b14.1.0b24.1.0rc04.1.0rc14.1.14.1.24.1.34.1.44.1.54.1.64.1.74.1.84.2.04.2.0a04.2.0a14.2.0a24.2.0b04.2.0b14.2.0b24.2.0b34.2.0rc04.2.14.2.24.2.34.2.44.2.54.2.64.2.74.3.04.3.0a04.3.0a1
4.5.7
jupyterlab
Ubuntu:25.10
 All versions, plus listed versions
4.0.11+ds1+~cs11.25.27-54.0.11+ds1+~cs11.25.27-64.0.11+ds1+~cs11.25.27-7
 None known
jupyterlab
Ubuntu:26.10
 All versions, plus listed versions
4.0.11+ds1+~cs11.25.27-94.4.10+ds1+~3.1.0+~0.16.6+~cs1.4.4-34.4.10+ds1+~3.1.0+~0.16.6+~cs1.4.4-4
 None known
jupyterlab
Ubuntu:26.04:LTS
 All versions, plus listed versions
4.0.11+ds1+~cs11.25.27-74.0.11+ds1+~cs11.25.27-84.0.11+ds1+~cs11.25.27-9
 None known
python-jupyterlab
openSUSE:Tumbleweed
From an advisory covering 3 CVEs
 before 4.5.7-1.1
4.5.7-1.1

History

History
RecordedChangedSources
affected, facts
first indexedCVE List, EUVD, GitHub Advisories, NVD, OSV

Dates are when Every CVE recorded each change. Upstream dates may differ.

In short

CVE-2026-42266 is a high vulnerability (CVSS 8.8) in Jupyter Jupyterlab, published May 5, 2026. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 5.65%, the 93rd percentile. Fixed in jupyterlab 4.5.7.

References

Show 14 moreShow less
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Left out here: 51 versions. The JSON record has them.

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