Cross-Site Scripting (XSS) in jupyterlab (CVE-2026-102830)
Summary
Cross-site scripting in jupyterlab (CVE-2026-102830). Confidential information can be exposed externally. Exploitable via jupyterlab. Mitigation: upgrade to 4.5.11 or later.
Original description
The description as published by the source.
Description
A language pack ships a Plural-Forms header saying how the language counts, for example nplurals=2; plural=(n != 1);. JupyterLab turns that string into a function with new Function, so the header gets executed. The check that meant to keep it safe was a regular expression. The regex was anchored at the start but not at the end, so it accepted any string that began with a valid plural rule and ignored everything after it.
A header such as the following passed the check, and the part after the plural rule ran in the JupyterLab page as soon as the first plural string was translated:
nplurals=2; plural=(n > 1);
Users are affected if all of the following are true:
- they run JupyterLab 3.0.0 through 4.6.3, or an application that bundles it such as Notebook 7;
- a language pack they did not write is installed in the environment; and
- that language is selected, so its catalogue is loaded
An installation using the default English locale loads no catalogue and is not affected.
CVE assignment pending, GitHub CNA is experiencing severe backlog
Impact
The code in the header ran in the JupyterLab page, in the same origin and session as the authenticated user. It could call the Jupyter Server REST API as that user: read and write any file under the server root, start a kernel and run code in it, and open a terminal where terminals are enabled. Nothing had to be clicked; translating one plural string was enough, and that happens during normal us…
Source: NIST National Vulnerability Database NVD GitHub Advisory
Auto-generated summary
Assembled by SecPulse from the source data (CVSS, CWE, affected versions) using templates — no AI involved. Check the original description and references below for exact details.
A vulnerability tracked as CVE-2026-102830 has been found in jupyterlab.
Attackers can target a specific entry point like jupyterlab over the network to misuse the product.
Confidential information can be exposed externally. CVSS score: 6.8/10.
What to do: upgrade jupyterlab to 4.5.11 or later.
If unsure, ask your IT team or search "jupyterlab CVE-2026-102830" on the vendor's site.
CVE-2026-102830 (jupyterlab) — CWE-79 / CVSS v3 6.8
Attack vector: remote (network-reachable) / unauthenticated
Attack surface: jupyterlab
Patched: 4.5.11 — apply immediately
Plan: 1) Audit SBOM/dependencies, 2) Stage→prod upgrade, 3) Add WAF/proxy monitoring on affected endpoints, 4) Hunt IOCs in logs.
Refs: see the GHSA / vendor advisory / patched release linked on this page.
Cross-site scripting (XSS) (CWE-79) exists in jupyterlab. Attackers reach the vulnerable code path via jupyterlab without authentication.
Check the vendor advisory for the affected versions of jupyterlab. Attack surface: jupyterlab.
Severity: Medium (CVSS 6.8/10). Confidential information can be exposed externally.
Update to 4.5.11.
Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.
Search webserver/proxy logs for unusual request patterns matching this CVE's known IOCs. Run grep -r 'jupyterlab' . against your dependency files (package-lock.json, requirements.txt, go.sum) to find affected services.
Response actions
Concrete steps and command examples for SOC/SRE teams to execute in order
-
1Identify exposure identify
grep -r 'jupyterlab' . | grep -v node_modulesリポジトリと本番環境の依存ファイル (package-lock.json / requirements.txt / go.sum / Gemfile.lock 等) で
jupyterlabを grep し、稼働しているサービス・バージョンを把握する。 -
2Apply patch patch
Upgrade jupyterlab to 4.5.11ステージング環境で 4.5.11 に上げて回帰テスト → 本番反映。回帰テストはアプリの主要ハッピーパスを含めること。
-
3Post-deployment verification verify
Confirm patched version is live in productionパッチ適用後、ステージングで PoC または同等の悪用パターンを再現して脆弱性が閉じたことを確認。本番ではアクセスログ・WAF でアラート再発が無いか継続監視。
Affected packages
Fix status by distribution
Fixed packages published by each distribution for this CVE
- Debian DEBIAN-CVE-2026-102830 jupyterlab
- Ubuntu UBUNTU-CVE-2026-102830 jupyterlab
References
- advisory nvd.nist.gov
- advisory github.com
- package github.com
- package pypi.org
- package pypi.org
- web github.com
- web github.com
- web github.com
- web github.com
- web github.com
- web github.com