LDAP Injection in Symfony: Prevention Guide with Code

Lightweight Directory Access Protocol (LDAP) is widely used for authentication and directory lookups. However, many Symfony-based web applications fail to validate and escape LDAP queries properly, leaving them vulnerable to LDAP injection attacks.

In this guide, we’ll explain what LDAP injection is, how it affects Symfony apps, and how to prevent it with secure code examples. Plus, we’ll show you how to use our Website Vulnerability Scanner online free to assess your site in seconds.

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🔍 What is LDAP Injection?

LDAP injection occurs when user-supplied input is directly inserted into an LDAP query without proper sanitization. This can allow an attacker to manipulate the query to retrieve unauthorized information or bypass authentication.

Example of a vulnerable LDAP query in Symfony:

// Vulnerable Symfony controller example
$username = $request->get('username');
$password = $request->get('password');

$ldapQuery = "(&(uid={$username})(userPassword={$password}))";
$result = $ldapConnection->search($ldapQuery);

If an attacker supplies *)(uid=*))(|(uid=*, they can manipulate the query to return all users.

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🚨 How to Detect LDAP Injection

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

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

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🔐 How to Prevent LDAP Injection in Symfony

Here are some secure coding practices for Symfony developers:

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✅ Use LDAP Escaping

Symfony provides a LdapEscaper class which escapes special LDAP characters properly.

use Symfony\Component\Ldap\Ldap;
use Symfony\Component\Ldap\LdapEscaper;

$username = $request->get('username');
$password = $request->get('password');

$escapedUsername = LdapEscaper::escape($username, '');
$escapedPassword = LdapEscaper::escape($password, '');

$ldapQuery = "(&(uid={$escapedUsername})(userPassword={$escapedPassword}))";
$result = $ldapConnection->search($ldapQuery);

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✅ Enforce Strong Input Validation

Before escaping, also validate inputs to allow only expected characters:

if (!preg_match('/^[a-zA-Z0-9_]+$/', $username)) {
    throw new \InvalidArgumentException('Invalid username format');
}

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✅ Use Parameterized Queries (if your LDAP library supports)

Some PHP LDAP libraries offer safer APIs. If available, prefer those.

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✅ Least Privilege LDAP Bind

Ensure the LDAP user your app uses has minimal permissions.

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🔗 Related Services You Can Explore

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Published on behalf of Pentest Testing Corp. — empowering you with cybersecurity knowledge.