CVE-2025-61669: Jupyter Server

Medium severity, CVSS 6.1. EPSS: 0.2% chance of exploitation in the next 30 days.

Jupyter Server is the backend for Jupyter web applications. In jupyter_server versions through 2.17.0, the next query parameter in the login flow is insufficiently validated in `LoginFormHandler._redirect_safe()`, which allows redirects to arbitrary external domains via values such as `///example.com`. An attacker can use a crafted login URL to redirect users to a malicious site and facilitate phishing attacks. This issue is fixed in version 2.18.0.

Affected products

• Jupyter Jupyter Server: before 2.18.0 (fixed in 2.18.0)

Published 2026-05-05. Last modified 2026-10-07.