Bug 2467453 (CVE-2026-40171)

Summary: CVE-2026-40171 Jupyter Notebook: JupyterLab: @jupyter-notebook/help-extension: @jupyterlab/help-extension: Jupyter Notebook and JupyterLab: Session takeover via stored cross-site scripting
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security <prodsec-ir-bot>
Status: NEW --- QA Contact:
Severity: high Docs Contact:
Priority: high    
Version: unspecifiedCC: jkoehler, lphiri, rjohnson
Target Milestone: ---Keywords: Security
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Hardware: All   
OS: Linux   
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A flaw was found in Jupyter Notebook and JupyterLab. A stored cross-site scripting (XSS) vulnerability in the help command linker can be exploited by an attacker who crafts a malicious notebook file. When a user interacts with this file, the XSS is triggered, allowing the attacker to steal authentication tokens. Successful exploitation can lead to a complete takeover of the Jupyter session, enabling arbitrary code execution and information disclosure.
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oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
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Bug Depends On: 2491384, 2491385    
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Description OSIDB Bzimport 2026-05-06 20:01:17 UTC 
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.