CVE-2026-42266Network attack vector

Authenticated code execution via extension allow-list bypass

Published May 13, 2026 · Updated May 13, 2026

Improper policy enforcement in JupyterLab 4.0.0 through 4.5.6 allows remote authenticated users to install unauthorized extensions. The PyPI Extension Manager accepts installations outside allowed_extensions_uris and the default PyPI index. Exposure requires an enabled default PyPI manager, an extension allow-list, and multi-tenant access; installed extension code can compromise the server.

CVSS severity8.8
High
EPSS probability0.63%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper policy enforcement in JupyterLab 4.0.0 through 4.5.6 allows remote authenticated users to install unauthorized extensions. The PyPI Extension Manager accepts installations outside allowed_extensions_uris and the default PyPI index. Exposure requires an enabled default PyPI manager, an extension allow-list, and multi-tenant access; installed extension code can compromise the server.

The record

CVE
CVE-2026-42266
Published
May 13, 2026
Updated
May 13, 2026
Vendor
Project Jupyter
Product
JupyterLab
Classifications
CWE-88, CWE-602, CWE-20, T1068
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. May 13, 2026CVE publishedPublication date reported by the CVE source.
  2. May 13, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=>= 4.0.0, < 4.5.7

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Project Jupyter · JupyterLabversion=>= 4.0.0, < 4.5.7

Published CVSS scores

8.8GitHubCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-88Improper Neutralization of Argument Delimiters in a Command ('Argument Injection')
CWE-602Client-Side Enforcement of Server-Side Security
CWE-20Improper Input Validation
T1068Exploitation for Privilege Escalation

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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