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CVE-2025-62800

CVE-2025-62800 · FastMCP vulnerable to reflected XSS in client's callback page

This page contains facts from public vulnerability sources. Check the original advisory before updating.

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 5.3 · Medium · EPSS 0.3% · Fix available

Published
Updated

Stack: python

Affected products and versions

  • fastmcp

    Versions
    • < 2.13.0: Affected

    No fix published

  • fastmcp PyPI

    Versions
    • 0.1.0
    • 0.2.0
    • 0.3.0
    • 0.3.1
    • 0.3.2
    • 0.3.3
    • 0.3.4
    • 0.3.5
    • 0.4.0
    • 0.4.1
    • 1.0
    • 2.0.0
    • 2.1.0
    • 2.1.1
    • 2.1.2
    • 2.10.0
    • 2.10.1
    • 2.10.2
    • 2.10.3
    • 2.10.4
    • 2.10.5
    • 2.10.6
    • 2.11.0
    • 2.11.1
    • 2.11.2
    • 2.11.3
    • 2.12.0
    • 2.12.0rc1
    • 2.12.1
    • 2.12.2
    • 2.12.3
    • 2.12.4
    • 2.12.5
    • 2.13.0rc1
    • 2.13.0rc2
    • 2.13.0rc3
    • 2.2.0
    • 2.2.1
    • 2.2.10
    • 2.2.2
    • 2.2.3
    • 2.2.4
    • 2.2.5
    • 2.2.6
    • 2.2.7
    • 2.2.8
    • 2.2.9
    • 2.3.0
    • 2.3.0rc1
    • 2.3.1
    • 2.3.2
    • 2.3.3
    • 2.3.4
    • 2.3.5
    • 2.4.0
    • 2.5.0
    • 2.5.1
    • 2.5.2
    • 2.6.0
    • 2.6.1
    • 2.7.0
    • 2.7.1
    • 2.8.0
    • 2.8.1
    • 2.9.0
    • 2.9.1
    • 2.9.2
    Affected ranges
    • ECOSYSTEM: < 2.13.0

    Update to 2.13.0

Original sources

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