The vulnerability stems from improper path sanitization when resolving user-controlled input (URL paths). While the exact implementation details aren't provided, directory traversal vulnerabilities in HTTP servers typically occur in the core request handling function that maps URLs to filesystem paths. The example attack shows the server processes URL paths with '../' sequences, indicating the file resolution logic lacks: 1) Path normalization checks, 2) Root directory confinement, and 3) Input sanitization. This pattern matches common Node.js server vulnerabilities where req.url is concatenated with a base directory without using safe path resolution libraries like path.resolve() with proper boundary checks.