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 PyPI Extension Manager was not contained to packages listed on the default PyPI index. This vulnerability is fixed in 4.5.7.
CVE-2026-42266
HIGHPre-NVD 8.88.8—
EchelonGraph scoreMEDIUM confidence
This high-severity CVE scores 8.8 under NVD CVSS v3. EPSS exploit probability: 0.5%, top 62% of all CVEs by exploit prediction. GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).
Triggered by: NVD CVSS baseline
Sources: epss, nvd
8.8
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
- High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS: 1%CVSS: 8.8Exploit: NoneExposed: 0
No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.
- CVSS v3
- 8.8
- EG Score
- 8.8(medium)
- EPSS
- 41.0%
- KEV
- Not listed
Published
May 13, 2026
Last Modified
July 8, 2026
Advisory Details (1)
Auto-updated May 13, 2026Patch available. Sources: github.
github Patch Available
Allowlist for PyPI Extension Manager not correctly enforced, PyPI Extension Manager not limited to default PyPI index · Advisory · jupyterlab/jupyterlab · GitHub
https://github.com/jupyterlab/jupyterlab/security/advisories/GHSA-37w4-hwhx-4rc4Vendor Advisories for CVE-2026-42266(1)
These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.
Affected Packages
(1 across 1 ecosystem)
PyPI(1)
| Package | Vulnerable range | Fixed in | Dependents |
|---|---|---|---|
| jupyterlab | 4.0.0 ... 4.5.6 (102 versions) | 4.5.7 | — |
Weakness Classification(2)
MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.
Frequently asked(5)
What is CVE-2026-42266?
CVE-2026-42266 is a high vulnerability published on May 13, 2026. 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 (allowedextensionsuris) is not correctly enforced by JupyterLab. The…
When was CVE-2026-42266 disclosed?
CVE-2026-42266 was first published in the National Vulnerability Database on May 13, 2026, with the most recent update on July 8, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-42266 actively exploited?
CVE-2026-42266 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 41.0% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.
What is the CVSS score of CVE-2026-42266?
CVE-2026-42266 has a CVSS v4.0 base score of 8.8 (CNA self-assessment; NVD's own analysis pending).
How do I remediate CVE-2026-42266?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-42266, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.
Dependency Blast Radius
See which npm, PyPI, Go, and Maven packages are affected by CVE-2026-42266
Is Your Infrastructure Affected by CVE-2026-42266?
EchelonGraph automatically scans your cloud infrastructure and maps CVE exposure using blast radius analysis.