CVE-2026-102830

JupyterLab: Cross-site scripting (XSS) in JupyterLab via crafted language package (jupyterlab.json)

Published Sep 29, 2026 CVSS 3.1 · 6.8 Medium EPSS < 1% KEV · Not listed
Description
JupyterLab is an extensible environment for interactive and reproducible computing, based on the Jupyter Notebook Architecture. From JupyterLab 3.0.0 until 4.5.11 and 4.6.4, and in JupyterLite Core 0.8.3 and earlier, the Plural-Forms header in a selected third-party language pack can append JavaScript after a valid plural rule because prefix-only regular-expression validation accepts a matching prefix without requiring the entire header to match. JupyterLab passes the accepted expression to new Function, so loading the catalogue and translating a plural string executes the appended code in the authenticated JupyterLab origin. Where Jupyter Server kernels, terminals, and APIs are exposed, the code can use authenticated server APIs to read or modify files and run code. Impact is much more limited in JupyterLite because it typically lacks most exposed Jupyter Server surfaces. The default English locale is unaffected because it does not load a translation catalogue. This issue is fixed in JupyterLab 4.5.11 and 4.6.4 and JupyterLite Core 0.8.4.

Remediation

No solution or workaround provided in the CVE record

Tracking

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Advisories

Source ID Title
Github GHSA Github GHSA GHSA-3jqq-pw4j-pqcj JupyterLab: Cross-site scripting (XSS) in JupyterLab via crafted language package (jupyterlab.json)
History
Type Values Removed Values Added
First Time appeared Jupyter
Jupyter jupyter Core
Jupyter jupyterlab
Vendors & Products Jupyter
Jupyter jupyter Core
Jupyter jupyterlab
Type Values Removed Values Added
Metrics ssvc

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

Type Values Removed Values Added
Description JupyterLab is an extensible environment for interactive and reproducible computing, based on the Jupyter Notebook Architecture. From JupyterLab 3.0.0 until 4.5.11 and 4.6.4, and in JupyterLite Core 0.8.3 and earlier, the Plural-Forms header in a selected third-party language pack can append JavaScript after a valid plural rule because prefix-only regular-expression validation accepts a matching prefix without requiring the entire header to match. JupyterLab passes the accepted expression to new Function, so loading the catalogue and translating a plural string executes the appended code in the authenticated JupyterLab origin. Where Jupyter Server kernels, terminals, and APIs are exposed, the code can use authenticated server APIs to read or modify files and run code. Impact is much more limited in JupyterLite because it typically lacks most exposed Jupyter Server surfaces. The default English locale is unaffected because it does not load a translation catalogue. This issue is fixed in JupyterLab 4.5.11 and 4.6.4 and JupyterLite Core 0.8.4.
Title JupyterLab: Cross-site scripting (XSS) in JupyterLab via crafted language package (jupyterlab.json)
Weaknesses CWE-79
CWE-94
References
Metrics cvssV3_1

{'score': 6.8, 'vector': 'CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:N'}

Weaknesses

Sources

Status
PUBLISHED
Assigner
GitHub_M
Published
Updated
Sep 29, 2026, 8:00 PM
Reserved
Sep 29, 2026, 5:25 PM
Status
Awaiting Analysis
Published
Sep 29, 2026, 7:17 PM
Modified
Sep 29, 2026, 9:40 PM
Severity
Moderate
Public date
Sep 29, 2026, 6:53 PM