Create middleware.js

src/middleware.js

@@ -0,0 +1,16 @@
+import { NextResponse } from "next/server";
+
+export function middleware(req) {
+  const host = req.headers.get("host");
+  const allowedHosts = ["localhost:3000"];
+
+  if (!host || !allowedHosts.includes(host)) {
+    return new NextResponse("Invalid Host header", { status: 400 });
+  }
+
+  return NextResponse.next();
+}
+
+export const config = {
+  matcher: "/api/:path*",
+};