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CVE-2026-40864

JupyterHub: Cross-origin form POSTs bypass XSRF

MEDIUM
4.3
CVSS Score
Published: May 22, 2026 at 08:13 PM UTC
Updated: July 23, 2026 at 07:32 PM UTC
2 products affected across 2 vendorsJupyterhubJupyterhub

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Severity
MEDIUM4.3
Exploit prediction
EPSS 0.1%
SSVC
No known exploit

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.

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

Jupyterhub· Jupyter
95%
4.1.0 ≤ v < 5.4.5
Affected range stops below 5.4.5, so it looks safe — our inference, not a vendor statement
Jupyterhub· Jupyterhub
60%
v < 5.4.5
Affected range stops below 5.4.5, so it looks safe — our inference, not a vendor statement

Remediation

No guide yet

No remediation guidance has been written for this CVE yet. What the record does show:

Patch and advisory references

References (2)

x_refsource_CONFIRMMitigationVendor Advisory
Source: cverecord
https://github.com/jupyterhub/jupyterhub/security/advisories/GHSA-m68r-v472-jgq9
x_refsource_MISCPatch
Source: cverecord
https://github.com/jupyterhub/jupyterhub/commit/9c5ec277d3cda5a59de2d8c8117efa77bd941127

SSVC — Action Prioritization

SSVCNo known exploitNot automatablePartial impact

SSVC signals action urgency (what to patch first), separate from CVSS which measures severity.

CVSS

4.3MEDIUM[email protected]
Attack Vector
NETWORK
Complexity
LOW
Privileges
NONE
User Interaction
REQUIRED
Scope
UNCHANGED
Confidentiality
NONE
Integrity
LOW
Availability
NONE
Vector?

Quick Info

StatusANALYZED
CWE
CWE-352

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