Skip to main content
VulnerabilityPublished Updated

CVE-2025-64340: FastMCP has a Command Injection vulnerability - Gemini CLI

Affects fastmcpSource GCVE Database

0
Compare
Authoritative record:CVE-2025-64340· Medium 6.7

Not known to be exploited · CVSS 6.7 Medium : upgrade to 3.2.0 when convenient.

Data as of 30 Oct 2026, 07:30 UTC

CVSS 3.1 base score
6.7Medium
How severe the flaw is on the 0–10 CVSS scale.
Patch
Available – fixed in 3.2.0
CVSS:3.1/AV:L/AC:H/PR:L/UI:R/S:U/C:H/I:H/A:H

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 3 Apr 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponized: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 29 Oct 2026.

What to do

Upgrade fastmcp to 3.2.0.

Affected software

ProductAffectedFixed in
Homebrewfastmcppkg:brew/fastmcpOther threatsAffected
  • >=2.12.3 <3.2.0
Fixed in
  • 3.2.0

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

Description

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. PoC: ```python from fastmcp import FastMCP mcp = FastMCP(name="test&calc") @mcp.tool def roll_dice(n_dice: int) -> list[int]: """Roll `n_dice` 6-sided dice and return the results.""" return [random.randint(1, 6) for _ in range(n_dice)] ``` ``` fastmcp install claude-code server.py # or: fastmcp install gemini-cli server.py ``` On Windows, this opens Calculator via the `&calc` in the server name. Impact: Arbitrary 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). Patched in #3522 by validating server names to reject shell metacharacters.

References

Community reviews

Loading reviews…