Fix NoSQL Injection in Symfony
NoSQL Injection in Symfony typically occurs when using Doctrine MongoDB ODM or raw drivers. Attackers exploit PHP's loose typing and the way Symfony handles request parameters to inject MongoDB operators like $gt, $ne, or $regex. If you pass an associative array from a request directly into a query filter, you're handing over control of your database logic to the client.
The Vulnerable Pattern
public function login(Request $request, DocumentManager $dm) { // Attacker sends JSON: {"username": {"$ne": null}, "password": {"$gt": ""}} $username = $request->get('username'); $password = $request->get('password');$user = $dm->getRepository(User::class)->findOneBy([ 'username' => $username, 'password' => $password ]); if ($user) { // Authentication bypassed because $ne and $gt logic returned the first user }
}
The Secure Implementation
The vulnerability stems from Doctrine ODM's flexibility: it accepts arrays as values to allow native MongoDB operators. When Symfony's Request object parses nested JSON or form-encoded arrays, it passes those arrays directly to the ODM. By forcing inputs to strings (or other expected scalars), you neutralize the injection because the ODM will treat the payload as a literal string value rather than a command object. Always validate input types using Symfony's Validator component or strict type-hinting before reaching the persistence layer.
public function login(Request $request, DocumentManager $dm) { // Force scalar types via explicit casting or Symfony Validator $username = $request->get('username'); $password = $request->get('password');if (!is_string($username) || !is_string($password)) { throw new BadRequestHttpException('Invalid input type'); } $user = $dm->getRepository(User::class)->findOneBy([ 'username' => (string) $username, 'password' => (string) $password ]); // Alternatively, use the Query Builder with explicit parameter types // $qb = $dm->createQueryBuilder(User::class) // ->field('username')->equals((string) $username) // ->field('password')->equals((string) $password);
}
Your Symfony API
might be exposed to NoSQL Injection
74% of Symfony apps fail this check. Hackers use automated scanners to find this specific flaw. Check your codebase before they do.
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