Jupyter Notebook Vulnerable to Authentication Token Theft via CommandLinker XSS
Impact
A stored Cross-Site Scripting (XSS) vulnerability in Jupyter Notebook allows attackers to steal authentication tokens from users who open malicious notebook files and interact with elements that the attacker can make look indistinguishable from legitimate controls (single click interaction).
The vulnerability enables complete account takeover through the Jupyter REST API, allowing the attacker to:
- Read all files
- Modify/create files
- Access running kernels and execute arbitrary code
- Create terminals for shell access
Patches
Jupyter Notebook 7.5.6 and JupyterLab 4.5.7 include patches for this vulnerability.
Workarounds
The help extension can be disabled via CLI:
jupyter labextension disable @jupyter-notebook/help-extension
jupyter labextension disable @jupyterlab/help-extensionHardening
The patched versions include a toggle to disable the command linker functionality altogether, for example via overrides.json:
{
"@jupyterlab/apputils-extension:sanitizer": {
"allowCommandLinker": false
}
}Resources
- https://jupyterlab.readthedocs.io/en/latest/user/commands.html#commands-in-markdown-output-and-files
Acknowledgments
Reported by Daniel Teixeira - NVIDIA AI Red Team
Affected software
Click a technology to see all vulnerabilities affecting it.
| Platform | Package | Vulnerable versions | Fixed in |
|---|---|---|---|
| npm package | @jupyterlab/help-extension | < 4.5.7 | 4.5.7 |
| npm package | @jupyter-notebook/help-extension | >= 7.0.0, < 7.5.6 | 7.5.6 |
| Python (PyPI) | jupyterlab | < 4.5.7 | 4.5.7 |
| Python (PyPI) | notebook | >= 7.0.0, < 7.5.6 | 7.5.6 |
References
- https://github.com/jupyter/notebook/security/advisories/GHSA-rch3-82jr-f9w9
- https://nvd.nist.gov/vuln/detail/CVE-2026-40171
- https://github.com/jupyter/notebook
- https://jupyterlab.readthedocs.io/en/latest/user/commands.html#commands-in-markdown-output-and-files
- https://pypi.org/project/jupyterlab
- https://github.com/advisories/GHSA-rch3-82jr-f9w9
- https://pypi.org/project/notebook
- CVSS vector
CVSS:4.0/AV:N/AC:L/AT:N/PR:H/UI:A/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N- Weakness (CWE)
CWE-601, CWE-79- Platform
- npm, Python (PyPI)
- Package
@jupyterlab/help-extension, @jupyter-notebook/help-extension, jupyterlab- Disclosed
- 30.04.2026
- Updated
- 11.10.2026 15:17
Sources and licenses
OSV / GitHub Advisory Database - PYSEC-2026-2538 - PyPA Advisory Database; CC BY 4.0
OSV / GitHub Advisory Database - PYSEC-2026-2682 - PyPA Advisory Database; CC BY 4.0
OSV / GitHub Advisory Database - GHSA-rch3-82jr-f9w9 - 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
-
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