koa-cors-error Module has fixed the bug when the system didn't send the 4xx or 5xx statuses through cross-domain requests. koa onerror method have been completely replaced. Installation $ npm install koa-cors-error Use var corsError = require('koa-cors-error'); app.use(cors());app.use(corsError()); app.use(function(ctx, next) { ctx.throw(400);});