CVE-2026-42266 | JupyterLab has an Extension Manager API/GUI Policy Discrepancy allowing 3rd party (malicious) extensions install via POST request.

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.

Published: 2026-05-13 Last update: 2026-05-26 Assigner: [email protected] Source: [email protected]
NVD Status：Analyzed，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2026-42266 is rated Low Risk (37.9/100): CVSS High severity, with low exploitation likelihood (EPSS 0.03%). Monitor for updates and reassess as exploit intelligence or EPSS changes.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Exploit prediction scoring system (EPSS) score for CVE-2026-42266

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-05-22 0.06% 0.03% -0.04%
2 2026-05-14 — 0.06% —

Full EPSS history (2 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2026-42266

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
8.8 3.1 HIGH
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:L)
A normal user session is enough; they don’t have to be admin.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:H)
Serious risk that confidential data gets exposed in a big way.
Integrity (I:H)
They could widely tamper with or forge data—trust in the data is badly hurt.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
 2.8 5.9 [email protected]

Weakness enumeration for CVE-2026-42266

GitHub Security Advisory for CVE-2026-42266

GHSA-37w4-hwhx-4rc4 · Severity: high · Ecosystem: pip — JupyterLab has an Extension Manager API/GUI Policy Discrepancy, allowing 3rd party (malicious) extensions install via POST request

OS Trackers for CVE-2026-42266

vendor priority summary link
debian not yet assigned CVE-2026-42266 not yet assigned priority: Debian including 1 source packages (jupyterlab), 3 status rows across 3 suites (forky, sid, trixie): open 3. https://security-tracker.debian.org/tracker/CVE-2026-42266
ubuntu medium CVE-2026-42266 medium priority: Ubuntu including 1 source packages (jupyterlab), 5 status rows across 5 suites (jammy, noble, questing, resolute, upstream): needs-triage 3, DNE 2. https://ubuntu.com/security/CVE-2026-42266

Affected software / configurations for CVE-2026-42266

Vendor Product Version Raw CPE
jupyter jupyterlab >= 4.0.0, < 4.5.7 cpe:2.3:a:jupyter:jupyterlab:*:*:*:*:*:*:*:*

References for CVE-2026-42266

cvelogic Threat Intelligence