How severe is CVE-2025-64340?

CVE-2025-64340 has a CVSS 3.x base score of 6.7, rated medium severity. It is exploitable over local access with high attack complexity, requires low privileges and user interaction. Impact on confidentiality is high, integrity high, and availability high.

Is CVE-2025-64340 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (53rd percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2025-64340?

CVE-2025-64340 affects Jlowin Fastmcp. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2025-64340?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.

Does CVE-2025-64340 have an EU (EUVD) identifier?

Yes. CVE-2025-64340 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2025-209207.

When was CVE-2025-64340 published?

CVE-2025-64340 was published on 2026-04-03 and last updated on 2026-07-24.

CVE-2025-64340

CVE-2025-64340 is a medium-severity vulnerability in Jlowin Fastmcp with a CVSS 3.x base score of 6.7. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-78.

Key facts

Severity: Medium (CVSS 3.x base score 6.7)
EPSS exploit prediction: 1% (53rd percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2025-209207
Weakness: CWE-78
Affected product: Jlowin Fastmcp
Published: 2026-04-03
Last modified: 2026-07-24

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.

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.
How severe is CVE-2025-64340?: CVE-2025-64340 has a CVSS 3.x base score of 6.7, rated medium severity. It is exploitable over local access with high attack complexity, requires low privileges and user interaction. Impact on confidentiality is high, integrity high, and availability high.
Is CVE-2025-64340 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (53rd percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2025-64340?: CVE-2025-64340 affects Jlowin Fastmcp. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2025-64340?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
Does CVE-2025-64340 have an EU (EUVD) identifier?: Yes. CVE-2025-64340 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2025-209207.
When was CVE-2025-64340 published?: CVE-2025-64340 was published on 2026-04-03 and last updated on 2026-07-24.

References

Affected products (1)

cpe:2.3:a:jlowin:fastmcp:*:*:*:*:*:*:*:*

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