CVE-2026-39313

MCP-Framework: Unbounded memory allocation in readRequestBody allows denial of service via HTTP transport

private async readRequestBody(req: IncomingMessage): Promise<any> {
    return new Promise((resolve, reject) => {
      let body = '';
      req.on('data', (chunk) => {
        body += chunk.toString();   // No size limit
      });
      req.on('end', () => {
        try {
          const parsed = body ? JSON.parse(body) : null;
          resolve(parsed);
        } catch (error) {
          reject(error);
        }
      });
      req.on('error', reject);
    });
  }

• Denial of Service: Any mcp-framework HTTP server can be crashed by a single large POST request to /mcp
• No authentication required: readRequestBody() executes before any auth checks (auth is opt-in, default is no auth)
• Dead config: maxMessageSize exists but is never enforced, giving a false sense of security
• Affected: All applications using mcp-framework HttpStreamTransport (60,000 weekly npm downloads)

CWE-770: Allocation of Resources Without Limits or Throttling
Suggested CVSS 3.1: 7.5 (AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H)

The application allocates resources such as memory, threads, or file descriptors based on untrusted input without enforcing a cap. Typical impact: resource exhaustion leading to denial of service.

Kodem intelligence

Already deployed Kodem?

Enforce maxMessageSize in readRequestBody():

private async readRequestBody(req: IncomingMessage): Promise<any> {
    const maxSize = this._config.maxMessageSize || 4 * 1024 * 1024;
    return new Promise((resolve, reject) => {
      let body = '';
      let size = 0;
      req.on('data', (chunk) => {
        size += chunk.length;
        if (size > maxSize) {
          req.destroy();
          reject(new Error('Request body too large'));
          return;
        }
        body += chunk.toString();
      });
      // ...
    });
  }

1. What is CVE-2026-39313? CVE-2026-39313 is a high-severity allocation of resources without limits or throttling vulnerability in mcp-framework (npm), affecting versions <= 0.2.21. It is fixed in 0.2.22. The application allocates resources such as memory, threads, or file descriptors based on untrusted input without enforcing a cap.
2. Which versions of mcp-framework are affected by CVE-2026-39313? mcp-framework (npm) versions <= 0.2.21 is affected.
3. Is there a fix for CVE-2026-39313? Yes. CVE-2026-39313 is fixed in 0.2.22. Upgrade to this version or later.
4. Is CVE-2026-39313 exploitable, and should I be worried? Whether CVE-2026-39313 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
5. What actually determines whether CVE-2026-39313 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.
6. How do I fix CVE-2026-39313? Upgrade mcp-framework to 0.2.22 or later.