CVE-2026-42266
Jupyterlab 4.0.0 – 4.5.7
Raw vector
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:HCVSS and EPSS are reproduced from their sources (NVD, FIRST EPSS). Risk Priority is our own derived reading, not an NVD score.
Summary
CVE-2026-42266 is a high-severity Argument Injection (CWE-88) vulnerability in Jupyter Jupyterlab. Its CVSS base score is 8.8 (High).
Operationally, exploitation aligns with the MITRE ATT&CK technique Command and Scripting Interpreter (T1059); ranked at the 49th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.
The strongest mitigations our analysis identified map to AC-25 (Reference Monitor) and AC-3 (Access Enforcement) — see the control section below for these in your framework.
OWASP Top 10 for Web (2025)
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2026-29995
Vulnerability Data
JupyterLab is an extensible environment for interactive and reproducible computing, based on the Jupyter Notebook Architecture. From 4.0.0 to 4.5.6, the allow-list of extensions that can be installed from PyPI Extension Manager (allowed_extensions_uris) is not correctly enforced by JupyterLab. The…
more
PyPI Extension Manager was not contained to packages listed on the default PyPI index. This vulnerability is fixed in 4.5.7.
- CWE(s)
Related Threats
MITRE ATT&CK Enterprise Techniques
CVEs Like This One
Affected Assets
Mitigating Controls
Control response
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V10.7.1V2.2.2V8.3.1V10.4.1
Mitigating Controls (NIST 800-53 r5) AI
Requires a tamper-proof, always-invoked reference monitor that cannot be bypassed by client-side logic.
Enforces all access decisions on the server according to policy rather than trusting client-supplied enforcement.
Enforces information-flow rules at the server boundary instead of delegating them to the client.
Developer testing can discover argument-injection flaws in command-construction code but does not stop their introduction.
Input validation directly stops construction of command strings containing unneutralized delimiters or injected arguments.
Monitors and controls all external and key internal interfaces so that server-side policy cannot be off-loaded to clients.
Mitigating Controls (NIST CSF 2.0) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→CSF cross-walk (authority under review) — links open the control.
Mitigating Controls (ISO/IEC 27001:2022 Annex A) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→ISO cross-walk (authority under review) — links open the control.
Secure development lifecycle mandates input validation and command construction practices that directly prevent argument injection.
Application security requirements include explicit rules for safe command-line argument handling and escaping.
Secure architecture principles discourage unsafe command invocation patterns and favor safer APIs.
Secure coding standards explicitly require proper neutralization of command arguments, directly eliminating CWE-88.
Security testing can detect argument injection but does not prevent it at the source.
Information access restriction is undermined when the client is trusted to enforce it.