GHSA-vmhf-c436-hxj4: JupyterLab Cross-Site Scripting Vulnerability

MODERATE
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CWE-84
Published
Advisory Summary

GHSA-vmhf-c436-hxj4 is a MODERATE cross-site scripting vulnerability (CWE-84: Improper Neutralization of Encoded URI Schemes in a Web Page) affecting JupyterLab libraries in the PyPI ecosystem. The issue involves stored xss in extension manager through package metadata unsanitized uri protocol. Remediation is available by upgrading affected packages to version 4.5.9.

GHSA-vmhf-c436-hxj4 at a Glance

CVE Identifier N/A
GHSA Identifier GHSA-vmhf-c436-hxj4
Severity MODERATE
CVSS v3.1 Base Score N/A
CWE Classification CWE-84: Improper Neutralization of Encoded URI Schemes in a Web Page
Affected Product JupyterLab
Package Ecosystem PyPI
Published Date
Last Updated

How to Fix GHSA-vmhf-c436-hxj4

To remediate this vulnerability, upgrade all affected JupyterLab dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

jupyterlab fixed: 4.5.9 
pip install jupyterlab>=4.5.9
Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

pip show jupyterlab

How to Check if You Are Affected

To determine whether your Python environment is affected by GHSA-vmhf-c436-hxj4, inspect your installed packages using pip:

pip show jupyterlab

Analyze the terminal output to locate any version of JupyterLab in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 4.5.9), your application is affected.

Note: The pip show jupyterlab command checks currently installed packages in your active Python environment.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-84: Improper Neutralization of Encoded URI Schemes in a Web Page, where the web application improperly neutralizes user-controlled input for executable script disguised with uri encodings. In JupyterLab, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

A malicious PyPI package can place a `javascript:` URL in its `[project.urls]` metadata. JupyterLab's Extension Manager renders this as the extension's home-page link without validating the protocol, so a user who clicks the extension name executes attacker-controlled JavaScript in the JupyterLab origin. ### Details One of the PyPI package's URL (jupyterlab/extensions/pypi.py) is copied straight into the `homepage_url` rendered by the frontend in packages/extensionmanager/src/widget.tsx#L77-L88. ```python best_guess_home_url = ( homepage_url # home_page / [project.urls] Homepage or data.get("project_url") or data.get("package_url") or documentation_url # docs_url / [project.urls] Documentation or source_url # [project.urls] Source Code or bug_tracker_url # bugtrack_url / [project.urls] Bug Tracker ) # homepage_url=best_guess_home_url ``` ```tsx {entry.homepage_url ? ( <a href={entry.homepage_url} target="_blank" rel="noopener noreferrer" ...> {entry.name} </a> ) : ( <div>{entry.name}</div> )} ``` ### Impact An attacker needs to publish a package to PyPI (no access to the target). When the package appears in a victim's extension manager list and the victim clicks the extension name, the payload runs in the JupyterLab origin. Preconditions: Extension Manager enabled with the default PyPI source, the malicious package appears in the victim's list/search results. ### Patches Patched in [4.5.9](https://github.com/jupyterlab/jupyterlab/releases/tag/v4.5.9), commits [4e61e07](https://github.com/jupyterlab/jupyterlab/commit/4e61e07d0a91145b53fbf96ac74b0387f6bc51f6) and [d5d961f](https://github.com/jupyterlab/jupyterlab/commit/d5d961f6e10a6442dddbf94d9a976b3897055a12)

GHSA-vmhf-c436-hxj4 Affected JupyterLab Versions

1 component(s)
Fixed Versions:
4.5.9
Product / Package Ecosystem Affected Versions Fixed Version
jupyterlab
pypi/jupyterlab
PyPI
< 4.5.9
4.5.9

References

GitHub Advisory / Wiki ADVISORY
https://github.com/jupyterlab/jupyterlab/security/advisories/GHSA-vmhf-c436-hxj4
Security Fix Commit FIX COMMIT
https://github.com/jupyterlab/jupyterlab/commit/4e61e07d0a91145b53fbf96ac74b0387f6bc51f6
Security Fix Commit FIX COMMIT
https://github.com/jupyterlab/jupyterlab/commit/d5d961f6e10a6442dddbf94d9a976b3897055a12
JupyterLab Source Repository REPOSITORY
https://github.com/jupyterlab/jupyterlab
JupyterLab Release RELEASE
https://github.com/jupyterlab/jupyterlab/releases/tag/v4.5.9

Frequently Asked Questions

What is GHSA-vmhf-c436-hxj4?
GHSA-vmhf-c436-hxj4 is a security vulnerability in JupyterLab involving Stored XSS in extension manager through package metadata unsanitized URI protocol under CWE-84: Improper Neutralization of Encoded URI Schemes in a Web Page.
Which JupyterLab versions are affected?
Affected versions include releases prior to 4.5.9 across affected packages: jupyterlab.
What version fixes GHSA-vmhf-c436-hxj4?
Upgrading to 4.5.9 (or the latest patched release for your respective branch) resolves the vulnerability.
Is jupyterlab affected?
Yes, jupyterlab is affected in releases prior to 4.5.9. Upgrade your dependency to 4.5.9 or later.
What CWE is associated with GHSA-vmhf-c436-hxj4?
GHSA-vmhf-c436-hxj4 is classified under CWE-84: Improper Neutralization of Encoded URI Schemes in a Web Page (The web application improperly neutralizes user-controlled input for executable script disguised with URI encodings.).
How can I check PyPI dependencies for GHSA-vmhf-c436-hxj4?
Run the dependency tree command: 'pip show jupyterlab'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-vmhf-c436-hxj4",
  "modified" : "2026-06-19T15:11:17Z",
  "published" : "2026-06-19T15:11:17Z",
  "aliases" : [ ],
  "summary" : "JupyterLab: Stored XSS in extension manager through package metadata unsanitized URI protocol",
  "details" : "A malicious PyPI package can place a `javascript:` URL in its `[project.urls]` metadata. JupyterLab's Extension Manager renders this as the extension's home-page link without validating the protocol, so a user who clicks the extension name executes attacker-controlled JavaScript in the JupyterLab origin.\n\n### Details\n\nOne of the PyPI package's URL (jupyterlab/extensions/pypi.py) is copied straight into the `homepage_url` rendered by the frontend in packages/extensionmanager/src/widget.tsx#L77-L88.\n\n```python\nbest_guess_home_url = (\n    homepage_url            # home_page / [project.urls] Homepage\n    or data.get(\"project_url\")\n    or data.get(\"package_url\")\n    or documentation_url    # docs_url / [project.urls] Documentation\n    or source_url           # [project.urls] Source Code\n    or bug_tracker_url      # bugtrack_url / [project.urls] Bug Tracker\n)\n\n# homepage_url=best_guess_home_url\n```\n\n```tsx\n{entry.homepage_url ? (\n  <a href={entry.homepage_url} target=\"_blank\" rel=\"noopener noreferrer\" ...>\n    {entry.name}\n  </a>\n) : ( <div>{entry.name}</div> )}\n```\n\n### Impact\n\nAn attacker needs to publish a package to PyPI (no access to the target). When the package appears in a victim's extension manager list and the victim clicks the extension name, the payload runs in the JupyterLab origin.\n\nPreconditions: Extension Manager enabled with the default PyPI source, the malicious package appears in the victim's list/search results.\n\n### Patches\nPatched in [4.5.9](https://github.com/jupyterlab/jupyterlab/releases/tag/v4.5.9), commits [4e61e07](https://github.com/jupyterlab/jupyterlab/commit/4e61e07d0a91145b53fbf96ac74b0387f6bc51f6) and [d5d961f](https://github.com/jupyterlab/jupyterlab/commit/d5d961f6e10a6442dddbf94d9a976b3897055a12)",
  "severity" : [ {
    "type" : "CVSS_V4",
    "score" : "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "PyPI",
      "name" : "jupyterlab"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "4.5.9"
      } ]
    } ],
    "database_specific" : {
      "last_known_affected_version_range" : "<= 4.5.8"
    }
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/jupyterlab/jupyterlab/security/advisories/GHSA-vmhf-c436-hxj4"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/jupyterlab/jupyterlab/commit/4e61e07d0a91145b53fbf96ac74b0387f6bc51f6"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/jupyterlab/jupyterlab/commit/d5d961f6e10a6442dddbf94d9a976b3897055a12"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/jupyterlab/jupyterlab"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/jupyterlab/jupyterlab/releases/tag/v4.5.9"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-84" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-06-19T15:11:17Z",
    "nvd_published_at" : null
  }
}