CVE-2026-40864mediumCWE-352

CVE-2026-40864: medium-severity vulnerability in jupyterhub

JupyterHub: Cross-origin form POSTs bypass XSRF

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33Vexday Risk Score

No sign of exploitation. It has a public proof of concept.

ssvc Attendcvss 5.4epss 0.1%
from disclosure to weapon22 days
Published on NVDMay 22
1st PoC+22d
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.
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:L
Affected products
jupyterhub · jupyterhub
⚠ Public resources, to assess the exposure of systems you control or are authorized to test. Test only with authorization.
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