Hash: SHA1

             AUSCERT External Security Bulletin Redistribution

                          ESB-2007.0956 -- [OSX]
             Apple Mail remote command execution vulnerability
                             28 November 2007


        AusCERT Security Bulletin Summary

Product:              Apple Mail
Publisher:            US-CERT
Operating System:     Mac OS X
Impact:               Execute Arbitrary Code/Commands
Access:               Remote/Unauthenticated

Original Bulletin:    http://www.kb.cert.org/vuls/id/433819

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Vulnerability Note VU#433819

Apple Mail remote command execution vulnerability


Apple Mail contains a vulnerability that may allow an attacker to execute
arbitrary commands on OS X Leopdard (10.5) systems.

I. Description

Apple OS X uses resource forks to store structured data in files. Data
forks are used to store unstructured data.

The AppleDouble standard is specified in RFC 1740:

      AppleDouble is the preferred format for a Macintosh file that is to
      be included in an Internet mail message, because it provides
      recipients with Macintosh computers the entire document, including
      icons and other Macintosh specific information, while other users
      easily can extract the Data fork (the actual data) as it is
      separated from the AppleDouble encoding.

Apple Mail parses resource forks in mail attachments that use the MIME
format AppleDouble.

- From the Heise Security report:

      Files on a Mac can contain additional information, such as the one
      that another program should be used to open them. The operating
      system stores these in the file system in a so-called "resource fork",
      which is linked to the file. This type of information is usually
      limited to the local system; however, for emails the MIME format
      AppleDouble allows resource forks to be attached -- these are
      automatically analyzed by Apple Mail.

      This allows an attacker to create an email with an attachment called
      picture.jpg that is displayed with a JPEG icon. But when the user
      tries to open the picture, Apple Mail analyses the resource fork and
      executes a shell script, for example, without further warning. In
      this case, even the MIME type displays the attachment as image/jpeg,
      but careful Mac users may become suspicious when they see that the
      picture is not immediately displayed as usual.

Note that to successfully exploit this vulnerability an attacker would need
to convince a user to open a specially crafted email attachment with Apple
Mail. Note that this vulnerability was originally addressed in
APPLE-SA-2006-03-01, but was not addressed or reintroduced in Mac OS X
Leopard. See US-CERT Technical Cyber Security Alert TA06-062A for more
information about APPLE-SA-2006-03-01.

II. Impact

A remote, unauthenticated attacker may be able to execute arbitrary
commands with the permissions of the user running Apple Mail.

III. Solution

We are currently unaware of a practical solution to this problem.

Do not open unsolicited email attachments

Use caution when opening email attachments. See US-CERT Cyber Security Tip
ST04-010 for more information on how to safely handle email messages.

Systems Affected

Vendor               Status     Date Updated
Apple Computer, Inc. Vulnerable 27-Nov-2007




This report was based on publicly available information provided by Heise

This document was written by Ryan Giobbi.

Other Information

Date Public          25/11/2007
Date First Published 27/11/2007 09:11:46
Date Last Updated    27/11/2007
CERT Advisory
CVE Name
Metric               9.28
Document Revision    32

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