CVE-2025-64340Public exploit

Command execution via shell-interpreted server names

Published Apr 3, 2026 · Updated Apr 3, 2026

OS command injection in FastMCP before 3.2.0 allows local users to execute commands through crafted server names on Windows. The Claude Code and Gemini CLI installers pass the name as a subprocess argument, but .cmd wrappers flatten it into a cmd.exe command that interprets shell metacharacters. Exploitation requires a user to install a crafted server while either target CLI is present as a .cmd wrapper; commands run with that user's privileges.

CVSS severity6.7
Medium
EPSS probability0.73%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

OS command injection in FastMCP before 3.2.0 allows local users to execute commands through crafted server names on Windows. The Claude Code and Gemini CLI installers pass the name as a subprocess argument, but .cmd wrappers flatten it into a cmd.exe command that interprets shell metacharacters. Exploitation requires a user to install a crafted server while either target CLI is present as a .cmd wrapper; commands run with that user's privileges.

The record

CVE
CVE-2025-64340
Published
Apr 3, 2026
Updated
Apr 3, 2026
Vendor
Prefect Technologies, Inc.
Product
FastMCP
Classifications
CWE-78, T1059.003
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Apr 3, 2026CVE publishedPublication date reported by the CVE source.
  2. Apr 3, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=< 3.2.0

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

Prefect Technologies, Inc. · FastMCPversion=< 3.2.0

Published CVSS scores

7.8NIST NVDCVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
6.7GitHub, Inc.CVSS:3.1/AV:L/AC:H/PR:L/UI:R/S:U/C:H/I:H/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-78Improper Neutralization of Special Elements used in an OS Command ('OS Command Injection')
T1059.003Windows Command Shell

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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