CVE-2025-64340
Medium
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.
SeverityMedium
CVSS6.7
Exploit probability—
ProductJlowin Fastmcp
PublishedApr 3, 2026
First seenApr 3, 2026
Weakness typeCWE-78OS command injection
How to fix
Update
- jlowin fastmcp3.2.0 or later
- fastmcp3.2.0 or later
Affected products
| Product | Affected versions | Fixed in |
|---|---|---|
| jlowin fastmcp | v < 3.2.0 | 3.2.0 |
| fastmcpPyPI | v < 3.2.0 | 3.2.0 |
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