Misconfigured CORS in express JS-D002

Cross-Origin Resource Sharing(CORS) is a mechanism that enables web browsers to perform cross-domain requests using the XMLHttpRequest API in a controlled manner. It defines the protocol to use between a web browser and a server to determine whether a cross-origin request is allowed.

Using *, null or google.com is not a reliable way to ensure security of the application or software.

Bad Practice

const express = require('express');
const app = express();
app.get('/', function (req, res) {
    res.writeHead(200, { 'Access-Control-Allow-Origin': '*' });
});

Recommended

const express = require('express');
const app = express();
app.get('/', function (req, res) {
    res.set('access-control-allow-origin', 'xyz.com');
});

References

• OWASP A05:2021 - Security Misconfiguration
• CWE-346 - Origin Validation Error
• CWE-942 - Overly Permissive Cross-domain Whitelist
• SANS Top 25 - Porous Defenses