SSRF Vulnerability in Symfony: Exploit & Prevention Guide

Server-Side Request Forgery (SSRF) is one of the most dangerous web application vulnerabilities today. If you’re using Symfony, you need to understand how this vulnerability arises and how to prevent it.

In this blog, we’ll explain SSRF with real Symfony code examples, demonstrate how attackers exploit it, and provide secure coding techniques to mitigate it.

We’ll also show you how to use our website vulnerability scanner online for free to identify this vulnerability instantly.

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🔍 What is SSRF?

Server-Side Request Forgery (SSRF) happens when a web application fetches data from a user-supplied URL without validating it. This enables attackers to:

• Access internal systems (e.g., cloud metadata)

• Conduct port scans on internal IPs

• Exploit trusted internal services

• Leak sensitive data to external hosts

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⚠️ Vulnerable Symfony Code Example

Here's a real Symfony controller vulnerable to SSRF:

// src/Controller/SSRFController.php
namespace App\Controller;

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

class SSRFController extends AbstractController
{
    public function fetchUrl(Request $request): Response
    {
        $url = $request->query->get('url'); // ⚠️ Unvalidated input

        $contents = file_get_contents($url); // ❌ SSRF vulnerable

        return new Response($contents);
    }
}

An attacker could run:

https://yourdomain.com/fetch-url?url=http://169.254.169.254/latest/meta-data

This accesses sensitive cloud metadata — a critical risk in cloud environments like AWS.

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🧪 Exploiting SSRF in Symfony

Example attack using curl:

curl 'https://victim.com/fetch-url?url=http://localhost:8080/admin'

Or to scan internal ports:

curl 'https://victim.com/fetch-url?url=http://127.0.0.1:22'

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✅ How to Prevent SSRF in Symfony

✔️ Validate and Whitelist URLs

$allowedHosts = ['api.safehost.com', 'example.org'];
$parsedUrl = parse_url($url);

if (!in_array($parsedUrl['host'], $allowedHosts)) {
    throw new \Exception("Blocked URL: SSRF protection triggered");
}

✔️ Block Internal IPs

function isInternalIp($ip) {
    return preg_match('/^(127|10|192\.168|172\.(1[6-9]|2[0-9]|3[0-1]))\./', $ip);
}

✔️ Use Symfony HttpClient Securely

use Symfony\Component\HttpClient\HttpClient;

$client = HttpClient::create();
$response = $client->request('GET', $url, [
    'headers' => ['User-Agent' => 'SecureAgent']
]);

$content = $response->getContent();

Always combine HttpClient with validation to ensure the URL is safe!

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

This screenshot shows the homepage of our website vulnerability scanner.

🖼️ Screenshot 2: Vulnerability Assessment Report

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

This report was generated using our free tool to check Website Vulnerability, showing SSRF and other vulnerabilities.

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📚 More Cybersecurity Blogs & Tutorials

We publish regular content on real-world vulnerabilities and how to secure your apps.

Visit our main blog here:
🔗 Pentest Testing Blog

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🧾 Summary

Feature	Description
Vulnerability	SSRF (Server-Side Request Forgery)
Framework	Symfony (PHP)
Detection	Input validation, IP filtering
Tools	HttpClient, parse_url()
Free Scan	https://free.pentesttesting.com
Pro Service	PentestTesting.com Services

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👋 Final Thoughts

SSRF in Symfony apps is dangerous but avoidable. Proper input validation, host whitelisting, and using safe HTTP clients can drastically reduce the risk. Use our free scanner to test your app or get in touch for expert pentesting.

Have feedback or questions? Let us know in the comments or share this post with fellow developers!