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.
Problem types
CWE-78: Improper Neutralization of Special Elements used in an OS Command ('OS Command Injection')
Product status
References
github.com/...astmcp/security/advisories/GHSA-m8x7-r2rg-vh5g
github.com/...astmcp/security/advisories/GHSA-m8x7-r2rg-vh5g
github.com/PrefectHQ/fastmcp/pull/3522