Prevent File Inclusion Vulnerability in Symfony

File Inclusion vulnerabilities can be disastrous for web applications, especially in high-level frameworks like Symfony. This blog will explore how these vulnerabilities occur, how they can be exploited, and most importantly—how you can prevent them with secure Symfony coding practices.

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📌 What is a File Inclusion Vulnerability?

File Inclusion is a type of vulnerability where an attacker can include files on a server through the web browser. It usually occurs when user input is not properly sanitized before being passed to file-related functions like require, include, or file_get_contents.

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🔥 Why Symfony Applications Can Be Vulnerable

While Symfony provides robust mechanisms for routing, templating, and input validation, developers often create custom routes or load dynamic files based on user input, leading to Local File Inclusion (LFI) or Remote File Inclusion (RFI).

👇 Risky Symfony Practice Example:

// src/Controller/FileViewController.php

namespace App\Controller;
use Symfony\Bundle\FrameworkBundle\Controller\AbstractController;
use Symfony\Component\HttpFoundation\Request;
use Symfony\Component\HttpFoundation\Response;

class FileViewController extends AbstractController
{
    public function view(Request $request): Response
    {
        $filename = $request->query->get('file');
        $content = file_get_contents('/var/www/html/files/' . $filename);
        return new Response($content);
    }
}

What's wrong?
If the URL is:

https://example.com/view?file=../../../../../etc/passwd

The attacker can read system files!

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✅ How to Prevent File Inclusion in Symfony

To avoid File Inclusion vulnerabilities, apply the following secure coding techniques:

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✅ 1. Strict Whitelisting

Only allow specific files to be accessed.

$allowedFiles = ['terms.txt', 'privacy.txt'];
$filename = $request->query->get('file');

if (!in_array($filename, $allowedFiles)) {
    throw new \Exception('Invalid file requested');
}

$content = file_get_contents('/var/www/html/files/' . $filename);

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✅ 2. Use Symfony Templating Instead of Manual Includes

Symfony Twig templates prevent arbitrary file inclusion by design.

// Safe rendering
return $this->render('static/privacy.html.twig');

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✅ 3. Validate and Sanitize All User Input

Never trust $_GET, $_POST, or Symfony's $request->query.

use Symfony\Component\Validator\Constraints as Assert;
use Symfony\Component\Validator\Validation;

$validator = Validation::createValidator();
$violations = $validator->validate($filename, [
    new Assert\Choice(['choices' => ['terms.txt', 'privacy.txt']])
]);

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🧪 Free Website Security Checker Tool

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📸 Screenshot of the Website Vulnerability Scanner Tool Webpage

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

📸 Screenshot of a Sample Website Vulnerability Assessment Report generated by the tool to check Website Vulnerability

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

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🔄 Additional Symfony Security Tips

• Disable remote file inclusion via php.ini:

  allow_url_include = Off
  

• Set strict permissions for included files.

• Keep Symfony and PHP up-to-date.

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🛠️ Sample Exploitation via Burp Suite

If vulnerable, an attacker might send a request like:

GET /view?file=../../../../etc/passwd HTTP/1.1
Host: victim.com

With Burp Suite, you can repeat and manipulate requests to probe for inclusion vulnerabilities.

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🚀 Web Application Penetration Testing Services

Need a deeper security review of your Symfony application? Our expert team at Pentest Testing Corp. offers a comprehensive Web App Penetration Testing Service that includes:

• Manual and automated vulnerability scanning

• Business logic testing

• Report with CVSS scoring and remediation advice

🔗 Learn more and book your test:
👉 https://www.pentesttesting.com/web-app-penetration-testing-services/

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📚 More Cybersecurity Blogs

Stay informed with the latest cybersecurity insights and tutorials on our blog:
👉 https://www.pentesttesting.com/blog/

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🏁 Conclusion

File Inclusion vulnerabilities in Symfony are a serious security concern—but they're 100% preventable with proper input validation, secure file handling, and adherence to Symfony's best practices.

Before deploying your app, run a free security scan. If you're serious about security, contact us for a professional penetration test today!