CVE-2026-54338: Jupyterhub

Medium severity, CVSS 5.3. EPSS: 0.4% chance of exploitation in the next 30 days.

JupyterHub is software that allows users to create a multi-user server for Jupyter notebooks. Prior to 5.5.0, invalid input to form-based login authenticators can place an unbounded attacker-controlled username in failed-login logs, allowing an unauthenticated attacker to consume logging and storage resources. This issue is fixed in version 5.5.0.

Affected products

• Jupyterhub Jupyterhub

Published 2026-08-07. Last modified 2026-09-09.