Security Advisory
CVE-2025-62800
6.1
MEDIUM
Vulnerability Description
FastMCP is the standard framework for building MCP applications. Versions prior to 2.13.0 have a reflected cross-site scripting vulnerability in the OAuth client callback page (oauth_callback.py) where unescaped user-controlled values are inserted into the generated HTML, allowing arbitrary JavaScript execution in the callback server origin. The issue is fixed in version 2.13.0.
Published Date
October 28, 2025
Official Source
NIST NVD Advisory