CVE-2026-33709: JupyterHub has an Open Redirect Vulnerability
Affected Version
JupyterHub <= 5.4.3
Impact
An open redirect vulnerability in JupyterHub <=5.4.3 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.
Patches
Upgrade to JupyterHub 5.4.4
Workarounds
A deployment can apply filters on the Location header in a reverse proxy such as nginx/apache/traefik.
Other sources
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.
— MITRE
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
pip/jupyterhubto a version that resolves this vulnerability.Fixed in 5.4.4 - Upgrade
Upgrade
JupyterHubto a version that resolves this vulnerability.Fixed in 5.4.4 - Configuration
Apply reverse-proxy filters on the Location header (nginx/apache/traefik) to prevent open-redirect style redirects outside JupyterHub.
Reverse proxy (nginx/apache/traefik) Location header filtering = Enable filter to block/validate Location header redirects to external attacker-controlled sites