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CVE-2025-62800
Good to know:
Date: October 28, 2025
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.
Severity Score
Severity Score
Weakness Type (CWE)
Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
CWE-79Top Fix
Upgrade Version
Upgrade to version fastmcp - 2.13.0;fastmcp - 2.13.0;https://github.com/jlowin/fastmcp.git - v2.13.0
CVSS v3.1
| Base Score: |
|
|---|---|
| Attack Vector (AV): | NETWORK |
| Attack Complexity (AC): | LOW |
| Privileges Required (PR): | LOW |
| User Interaction (UI): | NONE |
| Scope (S): | UNCHANGED |
| Confidentiality (C): | LOW |
| Integrity (I): | LOW |
| Availability (A): | LOW |