CVE-2025-62800

MEDIUM EPSS 16.2%
Published Oct 28, 20258mo ago · Modified Jun 17, 20261w ago
5.3 CVSS 4.0
Medium
Find Similar
Published Oct 28, 2025 8mo ago
Last Modified Jun 17, 2026 1w ago

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.

CVSS Details

Base Score
5.3
Exploitability
—
Impact
—
Vector string
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
Attack Vector Network
Attack Complexity Low
Privileges Required None
User Interaction P
Scope X

Threat Intelligence

EPSS Exploit Probability
16.2% percentile
Exploit & Patch Status
Public Exploit Known
No Patch Available

Weaknesses 1

CWE-79 Cross-site Scripting Injection

Affected Products 1

VendorProductVersionRange
jlowinfastmcp* <2.13.0

References 1

  • github.com https://github.com/jlowin/fastmcp/security/advisories/GHSA-mxxr-jv3v-6pgc
    ExploitThird Party Advisory

Remediation

No remediation data recorded yet

Check vendor advisories and the NVD entry for patch availability.