Skip to main content
← All vulnerabilities
CVE-2026-40864PYSEC-2026-2189BIT-JUPYTERHUB-2026-40864GHSA-M68R-V472-JGQ9

JupyterHub: Cross-origin form POSTs bypass XSRF

Published
Last modified
published
Not listed in CISA KEV
Fix
Fixed in 5.4.5
1 proof of concept on GitHub
  • Exploitation: none
  • Automatable: no
  • Technical impact: partial

Summary

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.

Timeline

  1. CVE published
  2. CISA SSVC assessment

    Exploitation: none · Automatable: no · Technical impact: partial

  3. Record last updated

Affected versions

  • jupyterhub jupyterhub

    From 4.1.0 · fixed in 5.4.5

  • jupyterhubPyPI

    From 4.1.0 · fixed in 5.4.5

References 3

GitHub · jupyterhub/jupyterhub

GitHub · romain-deperne/CVE-2026-40864