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CVE-2026-40864

JupyterHub: Cross-origin form POSTs bypass XSRF

Published: May 22, 2026Updated: Jun 1, 2026 Sources: CVE List NVDCWE-352
NVD MITRE
5.4CVSSMEDIUM
EPSS Score
0.2%
Top 95.1%
CISA KEV
Not in KEV
Exploits
No Known Exploits
Remediation
Patch Available

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.

CVSS Vector Breakdown

AV:NAC:LPR:NUI:RS:UC:NI:LA:L
Exploitability
AV:NAttack Vector
Network
AC:LAttack Complexity
Low
PR:NPrivileges Required
None
UI:RUser Interaction
Required
Scope
S:UScope
Unchanged
Impact
C:NConfidentiality
None
I:LIntegrity
Low
A:LAvailability
Low
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Weaknesses

CWE-352

Affected Products

jupyterhubjupyterhub
On-prem
AI / ML / notebook-mlops
jupyterhubjupyter
Mixed
AI / ML / notebook-mlops
jupyterhuboss-projectAI / MLaka oauthenticator, jupyter-server-proxy
jupyteross-projectAI / MLaka notebook, jupyter server, jupyterlab

Attack Graph

Products CVE Techniques Tactics

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Exploitability

Official Patch Available
Workaround Available

MITRE ATT&CK

1 technique
Initial Access
View detailed technique mapping

References

https://github.com/jupyterhub/jupyterhub/security/advisories/GHSA-m68r-v472-jgq9
github.com
https://github.com/jupyterhub/jupyterhub/commit/9c5ec277d3cda5a59de2d8c8117efa77bd941127
github.com

Timeline

Published
May 22, 2026
Last Updated
Jun 1, 2026

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