Security middleware is an intermediate request-processing layer that evaluates incoming requests before application logic runs. It can mark requests safe, flag them as suspicious, or block them outright, making it a central decision point in a broader security model. section 9.1.2
A production-oriented security middleware layer can:
- Analyze request frequency and patterns to detect brute-force attacks, denial-of-service attempts, and other unusual behavior. section 9.1.2
- Match requests against known attack signatures, including SQL injection and cross-site scripting patterns. section 9.1.2
- Validate authentication tokens and inspect headers or metadata for anomalies such as unusual user agents or IP addresses. section 9.1.2
- Apply machine-learning threat detection and rate-limit excessive requests before they reach backend services. section 9.1.2
Listing 9.2 Composable middleware
import { NextResponse } from 'next/server';
const composeMiddleware = (middlewares) => { #1
return async (request) => {
let response = NextResponse.next();
for (const middleware of middlewares) {
try {
const result =
await middleware(request, response); #2
if (result.response) return result.response;
if (result.continue === false) break;
} catch (error) {
console.error('Middleware error:', error);
return NextResponse.json(
{ error: 'Internal Server Error' },
{ status: 500 }
);
}
}
return response;
};
};
const middlewareChain = composeMiddleware([ #3
handleCORS,
rateLimit,
authenticate,
securityHeaders,
]);
export async function middleware(request) { #4
return await middlewareChain(request);
}
export const config = { #5
matcher: '/api/:path*',
};
A composable Next.js middleware chain runs CORS handling, rate limiting, authentication, and security headers in sequence; each middleware can continue, stop, return a response, or trigger a controlled error response. section 9.1.2
Place security middleware at the beginning of the request-processing pipeline so every request is intercepted before core logic. Keep it scalable for expected client load, and handle middleware failures without exposing internal errors. section 9.1.2 section 9.7
