{
"id": "GHSA-37w4-hwhx-4rc4",
"aliases": [
"CVE-2026-42266"
],
"details": "The allow-list of extensions that can be installed from PyPI Extension Manager (`allowed_extensions_uris`) is not correctly enforced by JupyterLab prior to 4.5.7. The PyPI Extension Manager was not contained to packages listed on the default PyPI index.\n\nThis has security implications for deployments that:\n- have allow-listed specific extensions with aim to prevent users from installing packages\n- have the kernel and terminals disabled or delegated to remote hosts (thus no access to install packages in the single-user server environment)\n- have multi-tenant deployments that is not configured for untrusted users (as per documented on JupyterHub https://jupyterhub.readthedocs.io/en/5.2.1/explanation/websecurity.html)\n- have the (default) PyPI Extension Manager enabled\n\n### Impact\n\nAn authenticated attacker - such as a student in a shared JupyterHub environment or a user in a multi-tenant JupyterLab deployment - can escalate their privileges. This might allow for data exfiltration, lateral movement within the network, and persistent compromise of the server infrastructure.\n\n### Patches\n\nJupyterLab [`v4.5.7`](https://github.com/jupyterlab/jupyterlab/releases/tag/v4.5.7) contains the patch.\n\nUsers of applications that depend on JupyterLab, such as Notebook v7+, should update `jupyterlab` package too.\n\n### Workarounds\n\nSwitch to read-only extension manager by adding the following command line option:\n\n```bash\n--LabApp.extension_manager=readonly\n```\n\nor the following traitlet:\n\n```python\nc.LabApp.extension_manager = 'readonly'\n```\n\nYou can confirm that the read-only manager is in use from GUI:\n\n<img width=\"293\" height=\"293\" alt=\"image\" src=\"https://github.com/user-attachments/assets/8016c809-633e-4ed0-a5bc-6bc4793caa0f\" />\n\nNote: configuration of a PyPI proxy with allow-listed packages is not sufficient to protect from this vulnerability.\n\n### References\n\n- allow-list https://jupyterlab.readthedocs.io/en/stable/user/extensions.html#listing-configuration\n- https://jupyterhub.readthedocs.io/en/5.2.1/explanation/websecurity.html\n- https://jupyterlab.readthedocs.io/en/latest/user/extensions.html#extension-manager-implementations",
"summary": "JupyterLab has an Extension Manager API/GUI Policy Discrepancy, allowing 3rd party (malicious) extensions install via POST request",
"affected": [
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "4.0.0"
},
{
"fixed": "4.5.7"
}
]
}
],
"package": {
"name": "jupyterlab",
"ecosystem": "PyPI"
},
"database_specific": {
"last_known_affected_version_range": "<= 4.5.6"
}
}
],
"modified": "2026-06-08T20:15:06Z",
"severity": [
{
"type": "CVSS_V3",
"score": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H"
}
],
"published": "2026-05-05T20:53:18Z",
"references": [
{
"url": "https://github.com/jupyterlab/jupyterlab/security/advisories/GHSA-37w4-hwhx-4rc4",
"type": "WEB"
},
{
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-42266",
"type": "ADVISORY"
},
{
"url": "https://github.com/jupyterlab/jupyterlab",
"type": "PACKAGE"
},
{
"url": "https://github.com/jupyterlab/jupyterlab/releases/tag/v4.5.7",
"type": "WEB"
},
{
"url": "https://github.com/pypa/advisory-database/tree/main/vulns/jupyterlab/PYSEC-2026-164.yaml",
"type": "WEB"
},
{
"url": "https://jupyterhub.readthedocs.io/en/5.2.1/explanation/websecurity.html",
"type": "WEB"
},
{
"url": "https://jupyterlab.readthedocs.io/en/latest/user/extensions.html#extension-manager-implementations",
"type": "WEB"
}
],
"schema_version": "1.4.0",
"database_specific": {
"cwe_ids": [
"CWE-20",
"CWE-602",
"CWE-88"
],
"severity": "HIGH",
"github_reviewed": true,
"nvd_published_at": "2026-05-13T16:16:47Z",
"github_reviewed_at": "2026-05-05T20:53:18Z"
}
}