CVE-2026-40864

JupyterHub: Cross-origin form POSTs bypass XSRF

Published May 22, 2026 CVSS 3.1 · 5.4 Medium EPSS < 1% KEV · Not listed
Description
JupyterHub is software that allows users to create a multi-user server for Jupyter notebooks. In versions 4.1.0 through 5.4.4, XSRF protection (updated in 4.1.0) inappropriately treated requests with Sec-Fetch-Mode: no-cors as same-origin requests, bypassing XSRF checks. The JSON API is not affected, only HTTP form endpoints, such as /hub/spawn and /hub/accept-share, meaning attackers could trigger server spawn (but not access the server) and if the attacker is a JupyterHub user permitted to share access to their server, cause a user to accept a share and have access to the attacker's server. This issue has been fixed in version 5.4.5. If developers are unable to immediately upgrade, they can temporarily mitigate this issue by dropping requests to JupyterHub with Sec-Fetch-Mode: no-cors if they are using a reverse proxy.

Remediation

No solution or workaround provided in the CVE record

Tracking

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Advisories

Source ID Title
Github GHSA Github GHSA GHSA-m68r-v472-jgq9 JupyterHub has cross-origin form POSTs bypass XSRF (CWE-352)
History
Type Values Removed Values Added
First Time appeared Jupyter
Jupyter jupyterhub
CPEs cpe:2.3:a:jupyter:jupyterhub:*:*:*:*:*:*:*:*
Vendors & Products Jupyter
Jupyter jupyterhub
Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Type Values Removed Values Added
First Time appeared Jupyterhub
Jupyterhub jupyterhub
Vendors & Products Jupyterhub
Jupyterhub jupyterhub
Type Values Removed Values Added
Description JupyterHub is software that allows users to create a multi-user server for Jupyter notebooks. In versions 4.1.0 through 5.4.4, XSRF protection (updated in 4.1.0) inappropriately treated requests with Sec-Fetch-Mode: no-cors as same-origin requests, bypassing XSRF checks. The JSON API is not affected, only HTTP form endpoints, such as /hub/spawn and /hub/accept-share, meaning attackers could trigger server spawn (but not access the server) and if the attacker is a JupyterHub user permitted to share access to their server, cause a user to accept a share and have access to the attacker's server. This issue has been fixed in version 5.4.5. If developers are unable to immediately upgrade, they can temporarily mitigate this issue by dropping requests to JupyterHub with Sec-Fetch-Mode: no-cors if they are using a reverse proxy.
Title JupyterHub: Cross-origin form POSTs bypass XSRF
Weaknesses CWE-352
References
Metrics cvssV3_1

{'score': 5.4, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:L'}

Weaknesses

Sources

Status
PUBLISHED
Assigner
GitHub_M
Published
Updated
May 26, 2026, 1:13 PM
Reserved
Apr 15, 2026, 3:57 PM
Status
Analyzed
Published
May 22, 2026, 9:16 PM
Modified
Jul 23, 2026, 11:10 AM