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CVE-2026-42557 critical CVSS 9.6

Cross-Site Scripting (XSS) in jupyterlab (CVE-2026-42557)

Summary

Cross-site scripting in jupyterlab (CVE-2026-42557). Successful exploitation can lead to full system takeover. Exploitable via button. Mitigation: upgrade to 4.5.7 or later.

Original description

The description as published by the source.

jupyterlab is an extensible environment for interactive and reproducible computing, based on the Jupyter Notebook Architecture. Prior to 4.5.7, JupyterLab's HTML sanitizer allowlists data-commandlinker-command and data-commandlinker-args on button elements, while CommandLinker listens for all click events on document.body and executes the named command without checking whether the element came from trusted JupyterLab UI. A notebook with a pre-saved HTML cell output containing a deceptive button can trigger arbitrary JupyterLab commands - including arbitrary code execution - on a single user click, without any code being submitted for execution by the user. This vulnerability is fixed in 4.5.7.

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-2026-42557 has been found in jupyterlab.
Attackers can target a specific entry point like button over the network to misuse the product.
Successful exploitation can lead to full system takeover. CVSS score: 9.6/10.
What to do: upgrade jupyterlab to 4.5.7 or later.
If unsure, ask your IT team or search "jupyterlab CVE-2026-42557" on the vendor's site.

CVE-2026-42557 (jupyterlab) — CWE-79 / CVSS v3 9.6
Attack vector: remote (network-reachable) / unauthenticated
Attack surface: button / CommandLinker / document.body / JupyterFrontEnd
Patched: 4.5.7 — 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.

❓ What is the problem

Cross-site scripting (XSS) (CWE-79) exists in jupyterlab. Attackers reach the vulnerable code path via button without authentication.

📍 Affected scope

Check the vendor advisory for the affected versions of jupyterlab. Attack surface: button / CommandLinker / document.body / JupyterFrontEnd.

🔥 Severity

Severity: Critical (CVSS 9.6/10). Successful exploitation can lead to full system takeover.

🔧 How to fix

Update to 4.5.7.

🛡️ Workaround

Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.

🔍 Detection

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

  1. 1
    Identify 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。

  2. 2
    Apply patch patch 
    Upgrade jupyterlab to 4.5.7

    ステージング環境で 4.5.7 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。

  3. 3
    Post-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

PyPI jupyterlab
[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"4.5.7"}]}]
PyPI notebook
[{"type":"ECOSYSTEM","events":[{"introduced":"7.0.0"},{"fixed":"7.5.6"}]}]
pip jupyterlab
[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"4.5.7"}]}]
pip notebook
[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"7.5.6"}]}]
Bitnami jupyter-base-notebook
[{"type":"SEMVER","events":[{"introduced":"7.0.0"},{"fixed":"7.5.6"}]}]
Bitnami jupyter-notebook
[{"type":"SEMVER","events":[{"introduced":"7.0.0"},{"fixed":"7.5.6"}]}]
Bitnami jupyterlab
[{"type":"SEMVER","events":[{"introduced":"0"},{"fixed":"4.5.7"}]}]

Fix status by distribution

Fixed packages published by each distribution for this CVE

References

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