CORS Misconfigurations in Laravel: A Security Risk You Must Fix

Introduction

Cross-Origin Resource Sharing (CORS) misconfigurations are one of the overlooked vulnerabilities in modern web applications, including those built with Laravel. Improper CORS configurations can expose your application to serious security threats, allowing attackers to access sensitive information from your server. In this blog, we will explore what CORS is, common misconfigurations in Laravel, their impact, and how to fix them. We will also provide coding examples to help you implement secure configurations.

Additionally, you can use our free Website Security Scanner tool to detect vulnerabilities in your application.

What is CORS?

CORS is a mechanism that allows resources on a web page to be requested from another domain outside the origin. It uses HTTP headers to determine whether a browser should permit the requested cross-origin access.

For example, a frontend application hosted at https://frontend.example.com may want to access data from an API hosted at https://api.example.com. If not configured securely, attackers could exploit this mechanism to steal sensitive data.

Common CORS Misconfigurations in Laravel

1. Allowing All Origins

Using the wildcard * in the Access-Control-Allow-Origin header is a common mistake. This configuration permits any domain to access your resources, leaving your application vulnerable.

header('Access-Control-Allow-Origin: *'); // Vulnerable configuration

2. Improper Configuration of HTTP Methods

Sometimes, developers allow all HTTP methods without restriction, which can lead to unauthorized actions.

header('Access-Control-Allow-Methods: GET, POST, PUT, DELETE, OPTIONS'); // Potentially insecure

3. Exposing Sensitive Headers

Allowing sensitive headers like Authorization in the Access-Control-Allow-Headers can enable attackers to misuse them.

Fixing CORS Misconfigurations in Laravel

Secure CORS Configuration

Laravel provides middleware to handle CORS securely. Install the package using Composer:

composer require fruitcake/laravel-cors

Once installed, configure your CORS settings in the config/cors.php file:

return [

    'paths' => ['api/*'], // Restrict to specific paths

    'allowed_methods' => ['GET', 'POST'], // Specify allowed methods

    'allowed_origins' => ['https://trusted-domain.com'], // Allow specific origins

    'allowed_headers' => ['Content-Type', 'X-Requested-With'], // Specify allowed headers

    'exposed_headers' => [],

    'max_age' => 0,

    'supports_credentials' => false, // Disallow credentials

];

This configuration ensures that only trusted domains can access specific API paths, minimizing the risk of exploitation.

Coding Example: Adding Custom CORS Middleware

For more control, you can create custom middleware to handle CORS in Laravel.

namespace App\Http\Middleware;

use Closure;

class CustomCorsMiddleware

{

    public function handle($request, Closure $next)

    {

        $response = $next($request);

        $response->headers->set('Access-Control-Allow-Origin', 'https://trusted-domain.com');

        $response->headers->set('Access-Control-Allow-Methods', 'GET, POST');

        $response->headers->set('Access-Control-Allow-Headers', 'Content-Type, X-Requested-With');

        return $response;

    }

}

Register this middleware in the app/Http/Kernel.php file:

protected $routeMiddleware = [

    'custom_cors' => \App\Http\Middleware\CustomCorsMiddleware::class,

];

Testing Your Website for Vulnerabilities

Before deploying your application, ensure it is free from vulnerabilities, including CORS misconfiguration.

Screenshot of the free tool homepage