CVE-2026-40171Jupyter Notebook and JupyterLab token theft via stored XSS in help command linker
Updated under an hour ago ()
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No exploitation reported and no EPSS estimate yet.
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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
- 8.4 HIGH (v4.0, CNA)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-79
- Known exploited
- Not in CISA's KEV catalog
- EPSS (exploitation in the next 30 days)
- Not loaded for this CVE
- Assigned by
- GitHub_M
- NVD analysis
- Awaiting Analysis
- Record last updated
- May 7, 2026
- First seen by InfoSec Signals
- Oct 9, 2026
Affected products
jupyter notebook jupyter:notebook (from the name) | from 7.0.0, <= 7.5.5 | CNA record |
jupyterlab help-extension jupyterlab:help_extension (from the name) | through 4.5.6 | CNA record |
jupyterlab jupyterlab jupyterlab:jupyterlab (from the name) | through 4.5.6 | CNA record |
jupyter-notebook help-extension jupyter_notebook:help_extension (from the name) | from 7.0.0,<= 7.5.5 | CNA record |
References
- https://github.com/jupyter/notebook/security/advisories/GHSA-rch3-82jr-f9w9x-refsource-confirm
The CVE record on cve.org NVD's entry
The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.