CVE-2025-64340
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.
Does this matter?
High impact if exploited, but EPSS currently rates exploitation as unlikely (0.73%). Schedule it in the normal patch cycle and watch for a rise in EPSS or a public exploit.
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 3.1
- 7.8 HIGHCVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
- EPSS
- 0.73% probability · 52th percentile
- CISA KEV
- Not listed
- Weakness
- CWE-78
- Affected
- jlowin/fastmcp
- Source
- security-advisories@github.com
References
- https://github.com/PrefectHQ/fastmcp/pull/3522Issue Tracking, Patch
- https://github.com/PrefectHQ/fastmcp/security/advisories/GHSA-m8x7-r2rg-vh5gExploit, Patch, Vendor Advisory
- https://github.com/PrefectHQ/fastmcp/security/advisories/GHSA-m8x7-r2rg-vh5gExploit, Patch, Vendor Advisory
Source: NVD record, EPSS from FIRST.org, KEV from CISA. Refreshed daily.