iDefense Security Advisory 03.21.11: Apple OfficeImport Framework Excel Memory Corruption Vulnerability

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iDefense Security Advisory 03.21.11
http://labs.idefense.com/intelligence/vulnerabilities/
Mar 21, 2011

I. BACKGROUND

The OfficeImport framework is an API used by Apple's mobile devices,
including the iPod Touch, iPhone, and iPad. The framework is used to
parse and display Microsoft Office file formats, such as Excel, Word,
and PowerPoint. The OfficeImport framework is used by several
applications, including MobileMail and MobileSafari. Both of these
applications are attack vectors for this vulnerability. For more
information, see the vendor's site found at the following link.

http://www.apple.com/iphone/softwareupdate/

II. DESCRIPTION

Remote exploitation of a memory corruption vulnerability in Apple Inc.'s
OfficeImport framework could allow an attacker to execute arbitrary code
with the privileges of the current user.

The vulnerability occurs when parsing an Excel file with a certain
maliciously constructed record. This record is used to describe a
formula that is shared between multiple cells. In this record, the
'formula' field is used to specify the formula used. By corrupting
certain opcodes within this formula it is possible to trigger a memory
corruption vulnerability. This can lead to the execution of arbitrary
code.

III. ANALYSIS

Exploitation of this vulnerability results in the execution of arbitrary
code with the privileges of the user opening the file. To exploit this
vulnerability, an attacker has several attack vectors. The most
dangerous vector is through MobileSafari, which will automatically open
and parse Office files embedded in Web pages. This behavior is similar
to Microsoft Office 2000 in that it enables drive-by style attacks
without any user-interaction beyond visiting a Web page (no file open
dialog is displayed, the file is simply opened). Additionally, an
attacker can e-mail a targeted user and attach a malicious file. The
user will then have to view the e-mail and attachment with MobileMail
to trigger the vulnerability.

IV. DETECTION

iDefense has confirmed the existence of this vulnerability in
OfficeFramework running on the following devices:

iPod Touch, IOS 3.1.3 iPad, IOS 3.2.2

Apple has reported Mac OS X and OS X Server 10.6 through 10.6.6
vulnerable.

V. WORKAROUND

iDefense is currently unaware of any workaround for this issue.

VI. VENDOR RESPONSE

Apple Inc. has released patches which addresses this issue. For more
information, consult their advisory at the following URL:

http://support.apple.com/kb/HT4581

VII. CVE INFORMATION

The Common Vulnerabilities and Exposures (CVE) project has assigned the
name CVE-2011-0184 to this issue. This is a candidate for inclusion in
the CVE list (http://cve.mitre.org/), which standardizes names for
security problems.

VIII. DISCLOSURE TIMELINE

01/07/2011  Initial Vendor Notification
01/07/2011  Initial Vendor Reply
03/21/2011  Coordinated Public Disclosure

IX. CREDIT

This vulnerability was reported to iDefense by Tobias Klein.

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X. LEGAL NOTICES

Copyright © 2011 Verisign

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Disclaimer: The information in the advisory is believed to be accurate
at the time of publishing based on currently available information. Use
of the information constitutes acceptance for use in an AS IS condition.
 There are no warranties with regard to this information. Neither the
author nor the publisher accepts any liability for any direct,
indirect, or consequential loss or damage arising from use of, or
reliance on, this information.