CVE-2025-62800

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.

CVSS v3 6.1 MEDIUM

6.1^/10

CVSS v3 : MEDIUM

Vector :

Exploitability : 2.8 / Impact : 2.7

Attack Vector NETWORK

Attack Complexity LOW

Privileges Required NONE

User Interaction REQUIRED

Confidentiality Impact LOW

Integrity Impact LOW

Availability Impact NONE

Scope CHANGED

References

Link	Resource
https://github.com/jlowin/fastmcp/security/advisories/GHSA-mxxr-jv3v-6pgc	Exploit Third Party Advisory
https://github.com/jlowin/fastmcp/security/advisories/GHSA-mxxr-jv3v-6pgc	Exploit Third Party Advisory

Configurations

Configuration 1 (hide)

cpe:2.3:a:jlowin:fastmcp:*:*:*:*:*:*:*:*

History

No history.

Information

Published : 2025-10-28 22:15

Updated : 2025-11-07 01:49

NVD link : CVE-2025-62800

Mitre link : CVE-2025-62800

CVE.ORG link : CVE-2025-62800

JSON object : View

Products Affected

jlowin

fastmcp

CWE

CWE-79

Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')

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