ZF2016-04: Potential remote code execution in zend-mail via Sendmail adapter

ZF2016-04: Potential remote code execution in zend-mail via Sendmail adapter

When using the zend-mail component
to send email via the ZendMailTransportSendmail transport, a malicious user
may be able to inject arbitrary parameters to the system sendmail program.
The attack is performed by providing additional quote characters within an
address; when unsanitized, they can be interpreted as additional command line
arguments, leading to the vulnerability.

The following example demonstrates injecting additional parameters to the
sendmail binary via the From address:

use ZendMail;

$mail = new MailMessage();
$mail->setBody('This is the text of the email.');

// inject additional parameters to sendmail command line
$mail->setFrom('"AAA" params injection"@domain', 'Sender's name');

$mail->addTo('hacker@localhost', 'Name of recipient');
$mail->setSubject('TestSubject');

$transport = new MailTransportSendmail();
$transport->send($mail);

The attack works because zend-mail filters the email addresses using
the RFC 3696 specification,
where the string "AAA" params injection"@domain is considered a valid
address. This validation is provided using the zend-validator component with
the following parameters:

ZendValidatorEmailAddress(
    ZendValidatorHostname::ALLOW_DNS | ZendValidatorHostname::ALLOW_LOCAL
)

The above accepts local domain with any string specified by double quotes as the
local part. While this is valid per RFC 3696, due to the fact that sender email
addresses are provided to the sendmail binary via the command line, they create
the vulnerability described above.

Action Taken

To fix the issue, we added a transport-specific email filter for the From
header in the Sendmail transport adapter. The filter checks for the sequence
" in the local part of the email From address.

$from = $headers->get('From');
if ($from) {
    foreach ($from->getAddressList() as $address) {
        if (preg_match('/\"/', $address->getEmail())) {
            throw new ExceptionRuntimeException("Potential code injection in From header");
        }
    }
}

The patch resolving the vulnerability is available in:

  • zend-mail, starting in version 2.7.2
  • zend-mail, 2.4.11
  • Zend Framework, 2.4.11

Zend Framework 2.5 and 3.0 versions will receive the update automatically, as
executing composer update in proejcts using these versions will update to
zend-mail
2.7.2+.

Acknowledgments

The Zend Framework team thanks the following for identifying the issues and
working with us to help protect its users:

  • The independent security researcher Dawid Golunski,
    who reported the vulnerability to Beyond Security’s SecuriTeam Secure
    Disclosure program;
  • Enrico Zimuel, who provided the patch.

Source: Zend security feed