Is CVE-2026-40864 actively exploited?

No active exploitation of CVE-2026-40864 has been confirmed so far. Continue monitoring, as exploit status can change.

Can CVE-2026-40864 be exploited remotely?

Yes. CVE-2026-40864 is exploitable remotely over the network (CVSS attack vector: Network).

What is the CVSS score of CVE-2026-40864?

CVE-2026-40864 has a CVSS score of 5.4 (MEDIUM).

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MEDIUM

CVE-2026-40864

CWE-352Published: May 22, 2026· Updated: May 26, 2026

5.4

CVSS v3.1

EPSS:0.01%probability of exploitation in 30 daysPercentile:3.3th

Official 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.

NVD Source

Technical Analysis

CVE-2026-40864 can be exploited remotely over the network without requiring physical or adjacent access, significantly expanding the attack surface for threat actors.

Exploitation does not require any privileges, though user interaction (Required) is needed, which slightly reduces the risk of mass automated attacks.