Understanding Host Header Injection in Laravel

In this blog post, we will explore Host Header Injection, a serious vulnerability in web applications, including Laravel-based ones. This vulnerability allows attackers to manipulate the host header in HTTP requests, leading to potential exploits such as cache poisoning, password reset poisoning, and open redirection. Let’s dive into the risks, a practical example, and prevention strategies.

What Is Host Header Injection?

Host Header Injection occurs when a web application blindly trusts the Host header supplied in HTTP requests. This vulnerability can lead to malicious activities like:

• Redirecting users to malicious websites.
• Tampering with password reset links.
• Manipulating server behavior.

Exploiting Host Header Injection in Laravel

Laravel applications are at risk if they rely on the Host header for critical decisions without validation. Let’s look at an example.

A Vulnerable Code Example:

// routes/web.php

use Illuminate\Support\Facades\Mail;

Route::get('/send-reset-link', function () {
    $user = User::where('email', '[email protected]')->first();

    if ($user) {
        $resetLink = 'http://' . $_SERVER['HTTP_HOST'] . '/reset-password?token=' . $user->reset_token;

        // Sending reset link
        Mail::to($user->email)->send(new \App\Mail\ResetPassword($resetLink));

        return "Password reset link sent.";
    }

    return "User not found.";
});

In this example, the application uses the Host header directly to generate a password reset link. An attacker can exploit this by crafting a malicious request:

GET /send-reset-link HTTP/1.1
Host: malicious.com

The generated reset link will point to malicious.com, potentially compromising the user.

Preventing Host Header Injection in Laravel

• Validate the Host Header Laravel provides an APP_URL environment variable that can be used to ensure a valid host:

// routes/web.php

Route::get('/send-reset-link', function () {
    $user = User::where('email', '[email protected]')->first();

    if ($user) {
        $resetLink = config('app.url') . '/reset-password?token=' . $user->reset_token;

        // Sending reset link
        Mail::to($user->email)->send(new \App\Mail\ResetPassword($resetLink));

        return "Password reset link sent.";
    }

    return "User not found.";
});

• Restrict Trusted Hosts Use Laravel’s trustedproxies middleware to restrict requests to trusted hosts. Update your config/trustedproxy.php:

return [
    'proxies' => '*',
    'headers' => [
        Request::HEADER_X_FORWARDED_ALL,
        Request::HEADER_FORWARDED,
    ],
    'host' => ['example.com'], // Add trusted hosts
];

• Secure Configurations Ensure your APP_URL in .env is correctly set:

APP_URL=https://yourdomain.com

Use Free Tools to Test for Vulnerabilities

You can use our free Website Security Scanner to test for Host Header Injection vulnerabilities.

Screenshot of the free tools webpage where you can access security assessment tools.

Additionally, after conducting a vulnerability assessment with our tool to check Website Vulnerability, you can generate a detailed report to understand your application’s security status.

An example of a vulnerability assessment report generated with our free tool, providing insights into possible vulnerabilities.

Conclusion

Host Header Injection is a critical vulnerability that can compromise the security of Laravel applications. By validating inputs, restricting trusted hosts, and using proper configurations, you can secure your application.

Test your website today with our Website Security Checker and take the first step towards securing your online presence.