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Medium · 6.7 CVE-2025-64340 EUVD-2025-209207GHSA-m8x7-r2rg-vh5gPYSEC-2026-2475

FastMCP has a Command Injection vulnerability - Gemini CLI

Published Apr 3, 2026 · Updated Apr 3, 2026 · Assigned by GitHub_M

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.

Affected products

VendorProductAffectedFixed
jlowin fastmcp < 3.2.0 —

Affected packages

EcosystemPackageAffectedFixedRecord
PyPI fastmcp < 3.2.0 3.2.0 GHSA-m8x7-r2rg-vh5g

References