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.
Published: 2026-09-29
Score: 6.8 Medium
EPSS: < 1% Very Low
KEV: No
Impact: n/a
Action: n/a
AI Analysis

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Remediation

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History

Wed, 30 Sep 2026 00:15:00 +0000

Type Values Removed Values Added
References
Metrics threat_severity

None

threat_severity

Moderate


Tue, 29 Sep 2026 20:30:00 +0000

Type Values Removed Values Added
Metrics ssvc

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


Tue, 29 Sep 2026 19:00:00 +0000

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'}


Subscriptions

No data.

cve-icon MITRE

Status: PUBLISHED

Assigner: GitHub_M

Published:

Updated: 2026-09-29T20:00:25.547Z

Reserved: 2026-09-29T17:25:25.265Z

Link: CVE-2026-102830

cve-icon Vulnrichment

Updated: 2026-09-29T20:00:17.309Z

cve-icon NVD

Status : Awaiting Analysis

Published: 2026-09-29T19:17:25.527

Modified: 2026-09-29T21:40:15.583

Link: CVE-2026-102830

cve-icon Redhat

Severity : Moderate

Publid Date: 2026-09-29T18:53:19Z

Links: CVE-2026-102830 - Bugzilla

cve-icon OpenCVE Enrichment

Updated: 2026-09-29T22:15:08Z

Weaknesses