id: PYSEC-2026-2475
published: "2026-07-13T14:36:46.084219Z"
modified: "2026-07-13T16:04:02.290801Z"
aliases:
- CVE-2025-64340
- GHSA-m8x7-r2rg-vh5g
summary: "FastMCP has a Command Injection vulnerability - Gemini CLI"
details: "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.\n\nPoC:\n```python\nfrom fastmcp import FastMCP\n\nmcp = FastMCP(name=\"test&calc\")\n\n@mcp.tool\ndef roll_dice(n_dice: int) -> list[int]:\n    \"\"\"Roll `n_dice` 6-sided dice and return the results.\"\"\"\n    return [random.randint(1, 6) for _ in range(n_dice)]\n```\n\n```\nfastmcp install claude-code server.py   # or: fastmcp install gemini-cli server.py\n```\n\nOn Windows, this opens Calculator via the `&calc` in the server name.\n\nImpact:\nArbitrary command execution with the privileges of the user running `fastmcp install`. Affects Windows hosts where the target CLI (one of claude, gemini) is installed as a `.cmd` wrapper. Does not affect macOS/Linux, and does not affect config-file-based install targets (cursor, goose, mcp-json).\n\nPatched in #3522 by validating server names to reject shell metacharacters."
affected:
- package:
    name: fastmcp
    ecosystem: PyPI
    purl: pkg:pypi/fastmcp
  ranges:
  - type: ECOSYSTEM
    events:
    - introduced: "0"
    - fixed: 3.2.0
  versions:
  - 0.1.0
  - 0.2.0
  - 0.3.0
  - 0.3.1
  - 0.3.2
  - 0.3.3
  - 0.3.4
  - 0.3.5
  - 0.4.0
  - 0.4.1
  - "1.0"
  - 2.0.0
  - 2.1.0
  - 2.1.1
  - 2.1.2
  - 2.10.0
  - 2.10.1
  - 2.10.2
  - 2.10.3
  - 2.10.4
  - 2.10.5
  - 2.10.6
  - 2.11.0
  - 2.11.1
  - 2.11.2
  - 2.11.3
  - 2.12.0
  - 2.12.0rc1
  - 2.12.1
  - 2.12.2
  - 2.12.3
  - 2.12.4
  - 2.12.5
  - 2.13.0
  - 2.13.0.1
  - 2.13.0.2
  - 2.13.0rc1
  - 2.13.0rc2
  - 2.13.0rc3
  - 2.13.1
  - 2.13.2
  - 2.13.3
  - 2.14.0
  - 2.14.1
  - 2.14.2
  - 2.14.3
  - 2.14.4
  - 2.14.5
  - 2.14.6
  - 2.14.7
  - 2.2.0
  - 2.2.1
  - 2.2.10
  - 2.2.2
  - 2.2.3
  - 2.2.4
  - 2.2.5
  - 2.2.6
  - 2.2.7
  - 2.2.8
  - 2.2.9
  - 2.3.0
  - 2.3.0rc1
  - 2.3.1
  - 2.3.2
  - 2.3.3
  - 2.3.4
  - 2.3.5
  - 2.4.0
  - 2.5.0
  - 2.5.1
  - 2.5.2
  - 2.6.0
  - 2.6.1
  - 2.7.0
  - 2.7.1
  - 2.8.0
  - 2.8.1
  - 2.9.0
  - 2.9.1
  - 2.9.2
  - 3.0.0
  - 3.0.0b1
  - 3.0.0b2
  - 3.0.0rc1
  - 3.0.0rc2
  - 3.0.0rc3
  - 3.0.1
  - 3.0.2
  - 3.1.0
  - 3.1.1
references:
- type: WEB
  url: https://github.com/PrefectHQ/fastmcp/security/advisories/GHSA-m8x7-r2rg-vh5g
- type: WEB
  url: https://github.com/jlowin/fastmcp/security/advisories/GHSA-m8x7-r2rg-vh5g
- type: ADVISORY
  url: https://nvd.nist.gov/vuln/detail/CVE-2025-64340
- type: WEB
  url: https://github.com/PrefectHQ/fastmcp/pull/3522
- type: PACKAGE
  url: https://github.com/PrefectHQ/fastmcp
- type: PACKAGE
  url: https://pypi.org/project/fastmcp
- type: ADVISORY
  url: https://github.com/advisories/GHSA-m8x7-r2rg-vh5g
severity:
- type: CVSS_V3
  score: CVSS:3.1/AV:L/AC:H/PR:L/UI:R/S:U/C:H/I:H/A:H