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.
History

Thu, 07 May 2026 21:45:00 +0000

Type Values Removed Values Added
First Time appeared Jupyter
Jupyter jupyterlab
Jupyter notebook
Jupyter-notebook
Jupyter-notebook help-extension
Jupyterlab
Jupyterlab help-extension
Vendors & Products Jupyter
Jupyter jupyterlab
Jupyter notebook
Jupyter-notebook
Jupyter-notebook help-extension
Jupyterlab
Jupyterlab help-extension

Thu, 07 May 2026 13:15:00 +0000

Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'total'}, 'version': '2.0.3'}


Wed, 06 May 2026 19:45:00 +0000

Type Values Removed Values Added
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.
Title Jupyter Notebook and JupyterLab token theft via stored XSS in help command linker
Weaknesses CWE-79
References
Metrics cvssV4_0

{'score': 8.4, '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'}


cve-icon MITRE

Status: PUBLISHED

Assigner: GitHub_M

Published:

Updated: 2026-05-07T12:25:06.041Z

Reserved: 2026-04-09T19:31:56.015Z

Link: CVE-2026-40171

cve-icon Vulnrichment

Updated: 2026-05-07T12:24:19.818Z

cve-icon NVD

Status : Awaiting Analysis

Published: 2026-05-06T20:16:31.857

Modified: 2026-05-07T15:07:32.390

Link: CVE-2026-40171

cve-icon Redhat

No data.