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Vulnerability record · CVE-2025-64340 · published 3 April 2026

CVE-2025-64340: Jlowin fastmcp os command injection vulnerability

Jlowin · Fastmcp

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.

7.8 CVSS 3.1 High EPSS 0.74% · top 47.4% CWE-78 · OS command injection
7.8CVSS 3.1 base score
0.74%EPSS exploitation probability, 30 days
NoNot in CISA KEV
1Affected product versions listed by NVD
3References, 2 tagged exploit
24 Jul 2026Last modified by NVD

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/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H

Affected products

1 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
https://github.com/PrefectHQ/fastmcp/pull/3522 Issue TrackingPatch
https://github.com/PrefectHQ/fastmcp/security/advisories/GHSA-m8x7-r2rg-vh5g ExploitPatchVendor Advisory
https://github.com/PrefectHQ/fastmcp/security/advisories/GHSA-m8x7-r2rg-vh5g ExploitPatchVendor Advisory

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Source: NIST National Vulnerability Database (record CVE-2025-64340), CISA KEV, FIRST EPSS (scores of 2026-09-26). This page is refreshed as NVD updates the record.