Summary
There was a recent CVE report on MCP: https://nvd.nist.gov/vuln/detail/CVE-2025-66416.
FastMCP does not use any of the affected components of the MCP SDK directly. However, FastMCP versions prior to 2.14.0 did allow MCP SDK versions <1.23 that were vulnerable to CVE-2025-66416. Users should upgrade to FastMCP 2.14.0 or later.
Impact
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
Remediation advice
Kodem Kai can prioritize this vulnerability in your dependency tree and generate a fix recommendation.
Frequently Asked Questions
- What is GHSA-RCFX-77HG-W2WV? GHSA-RCFX-77HG-W2WV is a high-severity security vulnerability in fastmcp (pip), affecting versions < 2.14.0. It is fixed in 2.14.0.
- Which versions of fastmcp are affected by GHSA-RCFX-77HG-W2WV? fastmcp (pip) versions < 2.14.0 is affected.
- Is there a fix for GHSA-RCFX-77HG-W2WV? Yes. GHSA-RCFX-77HG-W2WV is fixed in 2.14.0. Upgrade to this version or later.
- Is GHSA-RCFX-77HG-W2WV exploitable, and should I be worried? Whether GHSA-RCFX-77HG-W2WV is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether GHSA-RCFX-77HG-W2WV is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix GHSA-RCFX-77HG-W2WV? Upgrade
fastmcpto 2.14.0 or later.