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CVE-2026-33709: JupyterHub has an Open Redirect Vulnerability

• Severity: medium (CVSS 6.1 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.2% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-04-03 · updated 2026-07-24
• Weakness: CWE-601

Description

JupyterHub is software that allows one to create a multi-user server for Jupyter notebooks. Prior to version 5.4.4, an open redirect vulnerability in JupyterHub allows attackers to construct links which, when clicked, take users to the JupyterHub login page, after which they are sent to an arbitrary attacker-controlled site outside JupyterHub instead of a JupyterHub page, bypassing JupyterHub's check to prevent this. This issue has been patched in version 5.4.4.

Affected products

• jupyterhub: before 5.4.4 — fixed in 5.4.4

How to fix

Upgrade to a fixed version: jupyterhub 5.4.4. Check the vendor advisory for mitigations.

References

• https://github.com/jupyterhub/jupyterhub/releases/tag/5.4.4
• https://github.com/jupyterhub/jupyterhub/security/advisories/GHSA-3vff-hjqv-m7h8

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