CORS Misconfiguration

What is CORS?

Cross-Origin Resource Sharing (CORS) controls which domains can access your API. Misconfigured CORS policies can expose your API to unauthorized access or block legitimate requests.

Security Impact

Severity: Medium to High

• Unauthorized API access
• Data exposure
• Cross-origin attacks
• Credential theft

How to Fix

1. Configure CORS Middleware

Laravel 8+ includes built-in CORS support:

// config/cors.php
return [
    'paths' => ['api/*', 'sanctum/csrf-cookie'],
    
    'allowed_methods' => ['*'],
    
    'allowed_origins' => [
        'https://yourdomain.com',
        'https://app.yourdomain.com',
    ],
    
    'allowed_origins_patterns' => [],
    
    'allowed_headers' => ['*'],
    
    'exposed_headers' => [],
    
    'max_age' => 0,
    
    'supports_credentials' => true,
];

2. Never Use Wildcard with Credentials

// BAD - Security vulnerability
'allowed_origins' => ['*'],
'supports_credentials' => true,

// GOOD - Specific origins
'allowed_origins' => [
    'https://yourdomain.com',
    'https://app.yourdomain.com',
],
'supports_credentials' => true,

3. Environment-Specific Configuration

// config/cors.php
'allowed_origins' => explode(',', env('CORS_ALLOWED_ORIGINS', 'https://yourdomain.com')),

# .env
CORS_ALLOWED_ORIGINS=https://yourdomain.com,https://app.yourdomain.com

4. Restrict HTTP Methods

// Only allow necessary methods
'allowed_methods' => ['GET', 'POST', 'PUT', 'DELETE'],

// Don't use wildcard in production
'allowed_methods' => ['*'], // Avoid this

5. Install fruitcake/laravel-cors (Laravel 7 and below)

composer require fruitcake/laravel-cors
php artisan vendor:publish --tag="cors"

// app/Http/Kernel.php
protected $middleware = [
    \Fruitcake\Cors\HandleCors::class,
];

Verification Steps

1. Make API request from allowed origin - should succeed
2. Make request from unauthorized origin - should be blocked
3. Check response headers for proper CORS headers
4. Test preflight OPTIONS requests
5. Verify credentials are handled correctly

Common Scenarios

SPA with Same Domain

'paths' => ['api/*'],
'allowed_origins' => ['https://yourdomain.com'],
'supports_credentials' => true,

Multiple Subdomains

'allowed_origins_patterns' => ['/^https:\/\/.*\.yourdomain\.com$/'],
'supports_credentials' => true,

Public API

'allowed_origins' => ['*'],
'supports_credentials' => false, // Important!

Related Issues

• CSRF Protection
• Security Headers
• API Rate Limiting