CVE-2025-62800 — FastMCP vulnerable to reflected XSS in client's callback page
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 (…
Published: 2025-10-28 · CVSS: 5.3 · CVSS 4.0
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.
Source: CVE Program · Revision 8b16575c39f1e1810c5e863010da073d2d3285e7