CVE-2026-40171
Received
Received - Intake
Stored XSS in Jupyter Notebook and JupyterLab Help Extensions
Publication date: 2026-05-06
Last updated on: 2026-05-06
Assigner: GitHub, Inc.
Description
Description
In Jupyter Notebook versions 7.0.0 through 7.5.5, JupyterLab versions 4.5.6 and earlier, and the corresponding @jupyter-notebook/help-extension and @jupyterlab/help-extension packages before 7.5.6 and 4.5.7, a stored cross-site scripting issue in the help command linker can be chained with attacker-controlled notebook content to steal authentication tokens with a single click.
An attacker can craft a malicious notebook file containing elements that appear indistinguishable from legitimate controls and trigger execution when a user interacts with them. Successful exploitation allows theft of the user's authentication token and complete takeover of the Jupyter session through the REST API, including reading files, creating or modifying files, accessing kernels to execute arbitrary code, and creating terminals for shell access. This issue has been fixed in Notebook 7.5.6, JupyterLab 4.5.7, @jupyter-notebook/help-extension 7.5.6, and @jupyterlab/help-extension 4.5.7. As a workaround, disable the affected help extensions or set allowCommandLinker to false in the sanitizer configuration.
CVSS Scores
EPSS Scores
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Meta Information
Affected Vendors & Products
| Vendor | Product | Version / Range |
|---|---|---|
| jupyter | notebook | From 7.0.0 (inc) to 7.5.5 (inc) |
| jupyter | jupyterlab | to 4.5.6 (inc) |
| jupyter | notebook_help_extension | to 7.5.6 (exc) |
| jupyter | jupyterlab_help_extension | to 4.5.7 (exc) |
| jupyter | notebook | 7.5.6 |
| jupyter | jupyterlab | 4.5.7 |
| jupyter | notebook_help_extension | 7.5.6 |
| jupyter | jupyterlab_help_extension | 4.5.7 |
Helpful Resources
Exploitability
CWE
KEV
| CWE ID | Description |
|---|---|
| CWE-79 | The product does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users. |
Attack-Flow Graph
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