CVE-2025-64340 FastMCP has a Command Injection vulnerability - Gemini CLI
An attacker can execute arbitrary commands on Windows by providing server names with shell metacharacters during FastMCP installation.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- A user has to click or open something
- Fix
- Available
What is CVE-2025-64340?
CVE-2025-64340 is a medium-severity command injection vulnerability in jlowin fastmcp, published on 3 Apr 2026. It can only be exploited from the same machine or local network, and only if a user opens a file or follows a link.
Official 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.
Weakness: CWE-78
Which versions are affected by CVE-2025-64340?
3 open source packages ship an affected version, including fastmcp. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
fastmcp PyPI | All versions | 3.2.0 |
fastmcp PyPI | All versions | 3.2.0 |
fastmcp PyPI | All versions | 3.2.0 |
Products include Jlowin Fastmcp.
How do I fix CVE-2025-64340?
Upgrade fastmcp to 3.2.0 or later.
Upgrade, and pass arguments to programs as a list instead of through a shell. More about Command injection.
Is CVE-2025-64340 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2025-64340 exists.
Other vulnerabilities in jlowin fastmcp
- CVE-2026-32871 FastMCP OpenAPI Provider has an SSRF & Path Traversal Vulnerability
- CVE-2026-27124 FastMCP: Missing Consent Verification in OAuth Proxy Callback Facilitates Confused Deputy Vulnerabilities
- CVE-2025-69196 FastMCP OAuth Proxy token reuse across MCP servers
- CVE-2025-62801 FastMCP vulnerable to windows command injection in FastMCP Cursor installer via server_name
- CVE-2025-62800 FastMCP vulnerable to reflected XSS in client's callback page
Sources
Also known as CLSA-2026-1781139162, ECHO-8490-867c-f16b, GHSA-m8x7-r2rg-vh5g, PYSEC-2026-2475, ROOT-APP-PYPI-CVE-2025-64340.