mcp-framework is a framework for building Model Context Protocol (MCP) servers. In versions 0.2.21 and below, the readRequestBody() function in the HTTP transport concatenates request body chunks into a string with no size limit. Although a maxMessageSize configuration value exists, it is never enforced in readRequestBody(). A remote unauthenticated attacker can crash any mcp-framework HTTP server by sending a single large POST request to /mcp, causing memory exhaustion and denial of service. This issue has been fixed in version 0.2.22.

Affected: npm: mcp-framework

### Summary

The `readRequestBody()` function in `src/transports/http/server.ts` concatenates HTTP request body chunks into a string with no size limit, allowing a remote unauthenticated attacker to crash the server via memory exhaustion with a single large HTTP POST request.

### Details

**File:** `src/transports/http/server.ts`, lines 224-240

```typescript 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); }); } ```

A `maxMessageSize` configuration value exists in `DEFAULT_HTTP_STREAM_CONFIG` (4MB, defined in `src/transports/http/types.ts` line 124) but is never enforced in `readRequestBody()`. This creates a false sense of security.

### PoC

Local testing with 50MB POST payloads against the vulnerable `readRequestBody()` function:

| Trial | Payload | RSS growth | Time | Result | |-------|---------|-----------|------|--------| | 1 | 50MB | +197MB | 42ms | Vulnerable | | 2 | 50MB | +183MB | 46ms | Vulnerable | | 3 | 50MB | +15MB | 43ms | Vulnerable | | 4 | 50MB | +14MB | 32ms | Vulnerable | | 5 | 50MB | +65MB | 38ms | Vulnerable |

Reproducibility: 5/5 (100%)

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