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Public proof of conceptFix available

CVE-2025-64340

A public proof of concept exists; no exploitation attested.

  • Published2026-04-03
  • Fixed in3.2.0
  • WeaknessCWE-78

Am I affected?

With a domain, we read the version its public headers and pages expose. A distribution build can carry the fix under an older number.

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.

Timeline

dates in UTC
  1. 2026-04-0316:16CVE publishedNVD

Observed activity

isMalicious corpus · updated 2026-10-23 21:37 UTC
Indicators tagged with this CVE, per day0 indicators over 7 days
Block these indicators
  • Firewall list (EDL, text): https://api.ismalicious.com/edl/cve/CVE-2025-64340?format=txt
  • CSV export: https://api.ismalicious.com/edl/cve/CVE-2025-64340?format=csv
  • TAXII collection of exploited CVEs
  • The EDL and CSV take an API key on the Pro plan.

Versions per branch

NVD · OSV
Jlowin fastmcp
BranchAffectedFixed in
3.2< 3.2.03.2.0

as publishedRanges as NVD and OSV publish them; a distribution’s build can be fixed under an older number.

Fix

  1. Update Jlowin fastmcp to 3.2.0

Advisories and patches

Detection

Nuclei template
none so far
ProjectDiscovery
Exploit-DB
no entry
Exploit-DB
Proof-of-concept repositories
none listed
PoC-in-GitHub

Sources

  • CISA-ADPSSVC decisionpoc2026-04-03
  • OpenCVESSVC decisionpoc—
  • CNACVSS 3.16.7read 2026-10-23
  • NVDCVSS 3.17.8read 2026-10-23
  • CNAweakness (CWE)CWE-78read 2026-10-23
  • FIRST EPSSEPSS score0.7 %2026-10-23
  • OSVaffected packages—

Technical details

CVSS v3 Vector
CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
Published
2026-04-03
Last Modified
2026-07-24
NVD status
Analyzed

Frequently asked questions

What is CVE-2025-64340?

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.

Is CVE-2025-64340 actively exploited?

A proof-of-concept exploit exists for CVE-2025-64340, but active exploitation has not been confirmed at this time.

What is the CVSS score for CVE-2025-64340?

CVE-2025-64340 has a CVSS v3 base score of 7.8 (HIGH severity), with vector string CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H.

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