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Vulnerability · Published May 6, 2026 · Assigned by GitHub_M

CVE-2026-40171Jupyter Notebook and JupyterLab token theft via stored XSS in help command linker

High 8.4

In plain English

A high-severity cross-site scripting in notebook from jupyter. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.5% (higher than 41% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 4.0)8.4High
Exploit odds (30 days)0.5%top 58.7% of all CVEs
Exploited in the wildNo reportsCISA SSVC: none
Attack toolingNoneno public tooling known

Official 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.

Affected packages & fixed versions

EcosystemPackageFixed inAdvisory
Alpine:v3.24jupyter-notebook7.5.6-r0ALPINE-CVE-2026-40171
Debian:14jupyter-notebook7.4.7-3DEBIAN-CVE-2026-40171
Debian:13jupyterlabno fix listedDEBIAN-CVE-2026-40171
Debian:14jupyterlab4.4.10+ds1+~3.1.0+~0.16.6+~cs1.4.4-3DEBIAN-CVE-2026-40171
PyPIjupyterlab4.5.7GHSA-rch3-82jr-f9w9
PyPIjupyterlab4.5.7PYSEC-2026-2538
PyPInotebook7.5.6PYSEC-2026-2682
PyPInotebook7.5.6GHSA-rch3-82jr-f9w9
Ubuntu:25.10jupyter-notebookno fix listedUBUNTU-CVE-2026-40171
Ubuntu:26.10jupyter-notebookno fix listedUBUNTU-CVE-2026-40171
npm@jupyter-notebook/help-extension7.5.6GHSA-rch3-82jr-f9w9
npm@jupyterlab/help-extension4.5.7GHSA-rch3-82jr-f9w9

Affected products (as reported)

VendorProductVersions
jupyter notebook >=7.0.0, <= 7.5.5
jupyterlab help-extension <=4.5.6
jupyterlab jupyterlab <= 4.5.6
jupyter-notebook help-extension >=7.0.0,<= 7.5.5

Weakness: CWE-79 · 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

References