In PHP, the native mail() function uses the following signature:
The \r\n characters terminate the From: header prematurely and inject a new Bcc: header. The PHP mail() function (especially on older Unix sendmail systems) will honor this injected header, causing the server to send blind carbon copies of the contact form message to every address in the Bcc list.
// Secure sanitization example $email = filter_var($_POST['email'], FILTER_VALIDATE_EMAIL); if (!$email) die("Invalid email address provided."); // Remove newline characters to prevent header injection $name = str_replace(array("\r", "\n"), '', $_POST['name']); Use code with caution. 3. Escape Shell Arguments php email form validation - v3.1 exploit
Vulnerability Profile: PHP Email Validation Exploits (Ref: CVE-2016-10033 / 10045)
Are you currently trying to on a live server? In PHP, the native mail() function uses the
This article provides an in-depth, technical breakdown of how this specific exploit works, the underlying mechanics of PHP mail injection, and concrete steps to secure your forms against it. 1. What is the "PHP Email Form Validation - v3.1" Exploit?
use PHPMailer\PHPMailer\PHPMailer; use PHPMailer\PHPMailer\Exception; $mail = new PHPMailer(true); try $mail->setFrom($_POST['email'], $_POST['name']); // PHPMailer automatically sanitizes these fields $mail->addAddress('admin@example.com'); $mail->Subject = $_POST['subject']; $mail->Body = $_POST['message']; $mail->send(); catch (Exception $e) // Handle error safely Use code with caution. D. Implement CAPTCHA and Rate Limiting an attacker could:
The v3.1 exploit has significant implications for web applications that rely on PHP email form validation. If exploited, an attacker could: