CVE-2026-102830

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.

• CWE-79
• CWE-94

• https://github.com/jupyterlab/jupyterlab/commit/985a3223cd77fd4f991cd90066342a90711d70f6
• https://github.com/jupyterlab/jupyterlab/commit/de324ae91346c713c4f5e5485f97b6e914e0f774
• https://github.com/jupyterlab/jupyterlab/commit/f9de43dc565a1118120d466117f877a189a4ce90
• https://github.com/jupyterlab/jupyterlab/releases/tag/v4.5.11
• https://github.com/jupyterlab/jupyterlab/releases/tag/v4.6.4
• https://github.com/jupyterlab/jupyterlab/security/advisories/GHSA-3jqq-pw4j-pqcj

Published

Sep 29, 2026

Last Modified

Sep 29, 2026

Status

Awaiting Analysis

• How Strix found a critical auth bypass in etcdStrix autonomously discovered a critical authentication bypass in etcd, later designated CVE-2026-33413.
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