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CVE-2026-40864

CVE-2026-40864 · JupyterHub: Cross-origin form POSTs bypass XSRF

This page contains facts from public vulnerability sources. Check the original advisory before updating.

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 5.4 · Medium · EPSS 0.1% · Fix available

Published
Updated

Stack: system · python

Affected products and versions

  • jupyterhub

    Versions
    • >= 4.1.0, < 5.4.5: Affected

    No fix published

  • jupyterhub Debian:13

    Versions
    • 5.2.1+ds1-4
    • 5.2.1+ds1-5
    Affected ranges
    • ECOSYSTEM: (−∞, +∞)

    No fix published

  • jupyterhub Debian:14

    Versions
    • 5.2.1+ds1-4
    • 5.2.1+ds1-5
    Affected ranges
    • ECOSYSTEM: (−∞, +∞)

    No fix published

  • jupyterhub PyPI

    Versions
    • 4.1.0
    • 4.1.1
    • 4.1.2
    • 4.1.3
    • 4.1.4
    • 4.1.5
    • 4.1.6
    • 5.0.0
    • 5.0.0b1
    • 5.0.0b2
    • 5.1.0
    • 5.2.0
    • 5.2.1
    • 5.3.0
    • 5.3.0rc0
    • 5.4.0
    • 5.4.1
    • 5.4.2
    • 5.4.3
    • 5.4.4
    Affected ranges
    • ECOSYSTEM: ≥ 4.1.0, < 5.4.5

    Update to 5.4.5

  • jupyterhub Ubuntu:22.04:LTS

    Versions
    • 2.0.0+ds1-1
    • 2.0.0+ds1-2
    Affected ranges
    • ECOSYSTEM: (−∞, +∞)

    No fix published

  • jupyterhub Ubuntu:24.04:LTS

    Versions
    • 3.0.0+ds1-1
    Affected ranges
    • ECOSYSTEM: (−∞, +∞)

    No fix published

  • jupyterhub Ubuntu:25.10

    Versions
    • 5.2.1+ds1-2
    • 5.2.1+ds1-3
    • 5.2.1+ds1-4
    Affected ranges
    • ECOSYSTEM: (−∞, +∞)

    No fix published

  • jupyterhub Ubuntu:26.10

    Versions
    • 5.2.1+ds1-4
    • 5.2.1+ds1-5
    Affected ranges
    • ECOSYSTEM: (−∞, +∞)

    No fix published

  • jupyterhub Ubuntu:26.04:LTS

    Versions
    • 5.2.1+ds1-4
    Affected ranges
    • ECOSYSTEM: (−∞, +∞)

    No fix published

Original sources

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