#requestcontroller

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Detect SSRF in Symfony Apps – Free Security Checker

Server-Side Request Forgery (SSRF) is a critical web application vulnerability that occurs when an attacker is able to make the server perform unintended requests to internal or external systems. Symfony, while secure by design, can still be vulnerable to SSRF when insecure coding patterns are used.

In this post, we'll break down how SSRF works in Symfony, show coding examples, and share how you can detect it using our website vulnerability scanner online free.

🚨 What is SSRF and Why is it Dangerous?

SSRF occurs when a web server is tricked into sending a request to an unintended destination, including internal services like localhost, cloud metadata endpoints, or other restricted resources.

Impact of SSRF:

Internal network scanning

Accessing cloud instance metadata (AWS/GCP/Azure)

Bypassing IP-based authentication

🧑‍💻 SSRF Vulnerability in Symfony: Example

Here’s a simplified example in a Symfony controller where SSRF could be introduced:

// src/Controller/RequestController.php namespace App\Controller; use Symfony\Component\HttpFoundation\Request; use Symfony\Component\HttpFoundation\Response; use Symfony\Bundle\FrameworkBundle\Controller\AbstractController; class RequestController extends AbstractController { public function fetch(Request $request): Response { $url = $request->query->get('url'); // Unvalidated user input! // SSRF vulnerability: external requests with unsanitized user input $content = file_get_contents($url); return new Response($content); } }

⚠️ What’s wrong here?

The $url parameter comes directly from user input and is passed to file_get_contents() with no validation. This allows attackers to make arbitrary requests through your server.

✅ How to Fix It

Use a whitelist approach:

$allowedHosts = ['example.com', 'api.example.com']; $parsedUrl = parse_url($url); if (!in_array($parsedUrl['host'], $allowedHosts)) { throw new \Exception("Disallowed URL"); }

Better yet, avoid allowing user-defined URLs entirely unless absolutely necessary. Always sanitize and validate any user input that affects backend requests.

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💡 Real-World SSRF Exploitation: Metadata Services

In many cloud setups (like AWS), SSRF is used to access instance metadata services, such as:

curl http://169.254.169.254/latest/meta-data/

If the Symfony app allows attackers to proxy requests through the server, they can potentially leak AWS credentials!

🔍 Symfony + SSRF in HTTP Client

If you're using the HttpClient component:

use Symfony\Contracts\HttpClient\HttpClientInterface; public function __construct(HttpClientInterface $client) { $this->client = $client; } public function fetchUrl(string $url) { $response = $this->client->request('GET', $url); return $response->getContent(); }

Danger: Still vulnerable if $url is user-controlled.

Mitigation:

Validate and sanitize the input

Use allowlists

Block private IPs like 127.0.0.1, 169.254.169.254, etc.

📘 Learn More from Our Cybersecurity Blog

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📣 Conclusion

SSRF is a silent killer when left unchecked. Symfony developers must avoid directly using unvalidated input for server-side HTTP requests. You can:

Use input validation

Use whitelists

Block internal IP access

Test your applications regularly

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Stay secure. Stay informed. Follow us at https://www.pentesttesting.com/blog/ for more tips!

[magecomp]

Hey, Laravel Buddies!

Validation is a crucial step when collecting user data. Using a request controller, you can quickly validate in Laravel. The following prerequisites must be met in order to perform validation. Learn How to Add Form Validation in the Request Controller in Laravel

Complete Tutorial at Laravel: How to Add Form Validation in the Request Controller