Vulnerability Description
FastMCP is the standard framework for building MCP applications. Prior to version 3.2.0, server names containing shell metacharacters (e.g., &) can cause command injection on Windows when passed to fastmcp install claude-code or fastmcp install gemini-cli. These install paths use subprocess.run() with a list argument, but on Windows the target CLIs often resolve to .cmd wrappers that are executed through cmd.exe, which interprets metacharacters in the flattened command string. This issue has been patched in version 3.2.0.
CVSS Score
MEDIUM
Affected Products
| Vendor | Product | Versions |
|---|---|---|
| Jlowin | Fastmcp | < 3.2.0 |
Related Weaknesses (CWE)
References
- https://github.com/PrefectHQ/fastmcp/pull/3522Issue TrackingPatch
- https://github.com/PrefectHQ/fastmcp/security/advisories/GHSA-m8x7-r2rg-vh5gExploitPatchVendor Advisory
- https://github.com/PrefectHQ/fastmcp/security/advisories/GHSA-m8x7-r2rg-vh5gExploitPatchVendor Advisory
FAQ
What is CVE-2025-64340?
CVE-2025-64340 is a vulnerability with a CVSS score of 6.7 (MEDIUM). FastMCP is the standard framework for building MCP applications. Prior to version 3.2.0, server names containing shell metacharacters (e.g., &) can cause command injection on Windows when passed to fa...
How severe is CVE-2025-64340?
CVE-2025-64340 has been rated MEDIUM with a CVSS base score of 6.7/10. Review the CVSS metrics above for detailed severity breakdown.
Is there a patch for CVE-2025-64340?
Check the references section above for vendor advisories and patch information. Affected products include: Jlowin Fastmcp.