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    CVE-2026-40864

    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.

    Published:May 22, 2026
    Last Modified:Jun 1, 2026
    EPS:May 22, 2026
    EPSS Score:0.00016
    CVSS Score:5.4

    Affected Products

    Vendor
    Jupyter
    Product
    Jupyterhub
    Vendor
    Jupyterhub
    Product
    Jupyterhub

    Exploits

    https://github.com/romain-deperne/CVE-2026-40864

    Related CVEs

    CVE-2026-33709 (CVSS 5.1) — JupyterHub is software that allows one to create a multi-user server for Jupyter notebooks. Prior to version 5…
    CVE-2024-41942 (CVSS 7.2) — JupyterHub is software that allows one to create a multi-user server for Jupyter notebooks. Prior to versions …
    CVE-2024-28233 (CVSS 8.1) — JupyterHub is an open source multi-user server for Jupyter notebooks. By tricking a user into visiting a malic…
    CVE-2021-41247 (CVSS 3.5) — JupyterHub is an open source multi-user server for Jupyter notebooks. In affected versions users who have mult…
    CVE-2020-36191 (CVSS 4.5) — JupyterHub 1.1.0 allows CSRF in the admin panel via a request that lacks an _xsrf field, as demonstrated by a …
    CVE-2019-10255 (CVSS 6.1) — An Open Redirect vulnerability for all browsers in Jupyter Notebook before 5.7.7 and some browsers (Chrome, Fi…

    Common Vulnerability Scoring System

    Attack Vector
    Network
    Adjacent
    Local
    Physical
    Privileges Required
    None
    Low
    High
    User Interaction
    None
    Required
    Scope
    Unchanged
    Changed
    Confidentiality
    None
    Low
    High
    Integrity
    None
    Low
    High
    Availability
    None
    Low
    High