CVE-2026-40171
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.
Predictions
Heuristic predictions, AS-IS, for prioritization only.
Mitigations
No mitigations published for this CVE yet.
The vendor-content worker queues fetches as references arrive (check back in a few minutes). Or — if you've already worked around this in production — publish your fix to the community-verified tier.
✚ Propose a mitigation on Community → Mitigations published via the community go through AI scoring + 2 human reviewers + 7-day silent objection window before landing here withsource_tier=community-verified.
OS impact
Debian Affected 5 releases
| Version | Status | Fixed in |
|---|---|---|
| trixie | Affected | — |
| sid | Affected | — |
| forky | Affected | — |
| bullseye | Affected | — |
| bookworm | Affected | — |
Package impact
| Ecosystem | Package | Vulnerable | Fixed |
|---|---|---|---|
| npm | @jupyter-notebook/help-extension | >=7.0.0,<7.5.6 | 7.5.6 |
| PyPI | notebook | >=7.0.0,<7.5.6 | 7.5.6 |
| PyPI | jupyterlab | <4.5.7 | 4.5.7 |
| npm | @jupyterlab/help-extension | <4.5.7 | 4.5.7 |
| NPM | @jupyterlab/help-extension | <= 4.5.6 | 4.5.7 |
| PIP | jupyterlab | <= 4.5.6 | 4.5.7 |
| PIP | notebook | >= 7.0.0, <= 7.5.5 | 7.5.6 |
| NPM | @jupyter-notebook/help-extension | >= 7.0.0, <= 7.5.5 | 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://security-tracker.debian.org/tracker/CVE-2026-40171
- https://github.com/advisories/GHSA-rch3-82jr-f9w9
CWEs
CWE-79
Community-verified mitigations for this CVE will appear above when contributors publish them.
Verify integrity in audit chain (admin only). AS-IS.