Vulnerability · Published Sep 29, 2026 · Assigned by GitHub_M
CVE-2026-102830JupyterLab: Cross-site scripting (XSS) in JupyterLab via crafted language package (jupyterlab.json)
Medium 6.8
In plain English
A medium-severity cross-site scripting in jupyterlab from jupyterlab. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.3% (higher than 18% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Official 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.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian:13 | jupyterlab | no fix listed | DEBIAN-CVE-2026-102830 |
| Debian:14 | jupyterlab | no fix listed | DEBIAN-CVE-2026-102830 |
| PyPI | jupyterlab | 4.5.11 | GHSA-3jqq-pw4j-pqcj |
| PyPI | jupyterlab | 4.5.11, 4.6.4 | PYSEC-2026-4056 |
| PyPI | jupyterlab | 4.6.4 | GHSA-3jqq-pw4j-pqcj |
| PyPI | jupyterlite-core | 0.8.4 | PYSEC-2026-4059 |
| PyPI | jupyterlite-core | 0.8.4 | GHSA-3jqq-pw4j-pqcj |
| Ubuntu:26.04:LTS | jupyterlab | no fix listed | UBUNTU-CVE-2026-102830 |
| Ubuntu:26.10 | jupyterlab | no fix listed | UBUNTU-CVE-2026-102830 |
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| jupyterlab | jupyterlab | >= 3.0.0, < 4.5.11>= 4.6.0, < 4.6.4 |
| jupyterlab | jupyterlite-core | < 0.8.4 |
Weakness: CWE-79, CWE-94 · Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:N
References
- https://github.com/jupyterlab/jupyterlab/security/advisories/GHSA-3jqq-pw4j-pqcj x_refsource_CONFIRM
- https://github.com/jupyterlab/jupyterlab/commit/985a3223cd77fd4f991cd90066342a90711d70f6 x_refsource_MISC
- https://github.com/jupyterlab/jupyterlab/commit/de324ae91346c713c4f5e5485f97b6e914e0f774 x_refsource_MISC
- https://github.com/jupyterlab/jupyterlab/commit/f9de43dc565a1118120d466117f877a189a4ce90 x_refsource_MISC
- https://github.com/jupyterlab/jupyterlab/releases/tag/v4.5.11 x_refsource_MISC
- https://github.com/jupyterlab/jupyterlab/releases/tag/v4.6.4 x_refsource_MISC