CVE-2025-62800Medium· 6.1▾ SunlitFastMCP 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 ar…
▾ Sunlit zone — Low / medium · no exploitation signal
impact 33.6 · likelihood 0.1 · exploitation 0
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Exploit-prediction probability, daily snapshots since Jul 31.
Disclosure to exploitation, from the record and what we observed since indexing it.
Disclosed via NVD
0.3%
0.3% → 0.3%
Last analysed / modified upstream
— → 6.1
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.
fastmcp < 2.13.0Upgrade past the affected range:
fastmcp 2.13.0Affected packages:
fastmcp < 2.13.0Patched in:
fastmcp 2.13.0Field changes observed since this record was first indexed.
Connected by shared product, vendor, weakness, or advisory.
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