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Fencer Intel
medium 6.8

CVE-2026-102830 json

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

published last mo. modified last mo. also GHSA-3jqq-pw4j-pqcj , PYSEC-2026-4056 , PYSEC-2026-4059 , EUVD-2026-89337

cvss
6.8
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.3%
EPSS 0.3% chance of exploitation in 30 days, percentile 17%
public exploits
0
none known

Summary

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.

Patch / fix

  • pypi jupyterlab 4.5.11, 4.6.4
  • pypi jupyterlite-core 0.8.4
  • python-jupyterlab openSUSE Tumbleweed 4.5.11-1.1

opensuse advisories openSUSE-SU-2026:11945-1

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Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-102830 updated cvss 6.8

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

  • Red Hat Migration Toolkit for Applications 8 mta/mta-solution-server-rhel9
    affected: workaround, no fix planned “There are no known mitigations available for this vulnerability at this time. Red Hat recommends applying the available security update once it is released.”
  • Red Hat OpenShift AI (RHOAI) rhoai/odh-feature-server-rhel9, rhoai/odh-th-torch-cpu-py312-rhel9, rhoai/odh-th-torch-cuda-py312-rhel9, rhoai/odh-th-torch-rocm-py312-rhel9, rhoai/odh-th06-cpu-torch210-py312-rhel9, rhoai/odh-th06-cpu-torch291-py312-rhel9, +14 more
    affected: workaround, no fix available “There are no known mitigations available for this vulnerability at this time. Red Hat recommends applying the available security update once it is released.”

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
none
Automatable
no
Technical impact
total
Assessed
last mo.

Exploit prediction

0.26% chance of exploitation in the next 30 days, higher than 17% of all scored CVEs (FIRST EPSS, 2026-11-09).

CVSS scores

assigned by version score vector
CNA 3.1 6.8 CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:N
OSV 3.1 6.8 CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:N
GitHub 3.1 6.8 CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:N

Affected packages

ecosystem package affected fixed in
pypi jupyterlab
>=4.6.0, <4.6.4
>=3.0.0, <4.5.11
4.6.4
4.5.11
pypi jupyterlite-core
<0.8.4
0.8.4

Affected products

  • jupyterlab jupyterlab
  • jupyterlab jupyterlite-core

Classification

Weakness
  • CWE-79 Improper Neutralization of Input During Web Page Generation
  • CWE-94 Improper Control of Generation of Code
  • CWE-625 Permissive Regular Expression

References

Sources

Fencer Intel keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.