Cross-Site Request Forgery Vulnerability in JupyterHub by Project Jupyter
CVE-2026-40864

5.4MEDIUM

Key Information:

Vendor

Jupyterhub

Status
Jupyterhub
Vendor
CVE Published:
22 May 2026

Badges

👾 Exploit Exists🟡 Public PoC

What is CVE-2026-40864?

A Cross-Site Request Forgery vulnerability exists in JupyterHub versions 4.1.0 to 5.4.4, where the implementation of XSRF protection fails to properly validate requests flagged with Sec-Fetch-Mode: no-cors. This allows attackers to bypass XSRF safeguards on HTTP form endpoints, notably /hub/spawn and /hub/accept-share. Although this vulnerability does not provide direct access to the server, it could enable an attacker with shared access to hijack user sessions, invoking unwanted server spawning actions. The issue is resolved in JupyterHub version 5.4.5, while temporary mitigations can be applied via reverse proxy configurations.

Affected Version(s)

jupyterhub >= 4.1.0, < 5.4.5

Exploit Proof of Concept (PoC)

PoC code is written by security researchers to demonstrate the vulnerability can be exploited. PoC code is also a key component for weaponization which could lead to ransomware.

CVE-2026-40864
Created by romain-deperne

References

https://github.com/jupyterhub/jupyterhub/security/advisor...
x_refsource_CONFIRM
https://github.com/jupyterhub/jupyterhub/commit/9c5ec277d...
x_refsource_MISC

CVSS V3.1

Score:
5.4
Severity:
MEDIUM
Confidentiality:
None
Integrity:
Low
Availability:
None
Attack Vector:
Network
Attack Complexity:
Low
Privileges Required:
None
User Interaction:
Required
Scope:
Unchanged

Timeline

  • 🟡

    Public PoC available

  • 👾

    Exploit known to exist

  • Vulnerability published

  • Vulnerability Reserved

.