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MEDIUM

CVE-2026-102830

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

CVSS v3

6.8

MEDIUM

EPSS Score

0.3 %

exploit probability, as of 2026-10-19

CISA KEV

No

known exploited

Exploitation

none

SSVC status

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Affected and fixed versions

Packages from OSV.dev and products from the vendors' CSAF advisories.

version not verifiedVersions not verified: read as OSV.dev and the vendors publish them, not checked against each vendor's release list.

Packages

  • jupyterlabPyPIfrom 3.0.0 · fixed in 4.5.11
  • jupyterlite-corePyPIall versions · fixed in 0.8.4

Vendor advisories

  • CVE-2026-102830 Red Hat Product Security21 known affected

    jupyterlab: jupyterlite-core: JupyterLab: Arbitrary code execution via crafted language pack

    mta/mta-solution-server-rhel9 as a component of Migration Toolkit for Applications 8 · rhoai/odh-feature-server-rhel9 as a component of Red Hat OpenShift AI (RHOAI) · rhoai/odh-th-torch-cpu-py312-rhel9 as a component of Red Hat OpenShift AI (RHOAI)

Full record on NVD

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.

Technical details

CVSS v3 Vector
CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:N
Published
2026-09-29
Last Modified
2026-09-29

Frequently asked questions

What is 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.

Is CVE-2026-102830 actively exploited?

Active exploitation of CVE-2026-102830 has not been confirmed. Its EPSS score was 0.3% on 2026-10-19, the estimated probability of exploitation in the next 30 days.

What is the CVSS score for CVE-2026-102830?

CVE-2026-102830 has a CVSS v3 base score of 6.8 (MEDIUM severity), with vector string CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:N.

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