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

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-102830
StatePUBLISHED
AssignerGitHub_M
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-09-29 19:17:25 UTC
Updated2026-09-29 21:40:15 UTC
DescriptionJupyterLab 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.

Risk And Classification

Primary CVSS: v3.1 6.8 MEDIUM from [email protected]

CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:N

Problem Types: CWE-79 | CWE-94 | CWE-79 CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') | CWE-94 CWE-94: Improper Control of Generation of Code ('Code Injection')

VersionSourceTypeScoreSeverityVector
3.1[email protected]Secondary6.8MEDIUMCVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:N
3.1CNADECLARED6.8MEDIUMCVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:N

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
High
Privileges Required
None
User Interaction
Required
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
None

CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:N

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Jupyterlab Jupyterlab affected >= 3.0.0, < 4.5.11 Not specified
CNA Jupyterlab Jupyterlab affected >= 4.6.0, < 4.6.4 Not specified
CNA Jupyterlab Jupyterlite-core affected < 0.8.4 Not specified

References

ReferenceSourceLinkTags
github.com/jupyterlab/jupyterlab/commit/f9de43dc565a1118120d466117f877a1... [email protected] github.com
github.com/jupyterlab/jupyterlab/commit/985a3223cd77fd4f991cd90066342a90... [email protected] github.com
github.com/jupyterlab/jupyterlab/releases/tag/v4.5.11 [email protected] github.com
github.com/jupyterlab/jupyterlab/releases/tag/v4.6.4 [email protected] github.com
github.com/jupyterlab/jupyterlab/security/advisories/GHSA-3jqq-pw4j-pqcj [email protected] github.com
github.com/jupyterlab/jupyterlab/commit/de324ae91346c713c4f5e5485f97b6e9... [email protected] github.com
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