iDefense Security Advisory 11.11.10: Apple Mobile OfficeImport Framework Excel Parsing Memory Corruption Vulnerability

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iDefense Security Advisory 11.11.10
http://labs.idefense.com/intelligence/vulnerabilities/
Nov 11, 2010

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 maliciously
constructed Excel record. Specific values within this record can
trigger a memory corruption vulnerability, and result in values from
the file being used as function pointers. This allows an attacker to
execute 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 email a targeted user and attach a malicious file. The
user will then have to view the email 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 3.2.1

Apple has confirmed Mac OS X and Mac OS X Server v10.6 through v10.6.4
to be vulnerable.

V. WORKAROUND

iDefense is currently unaware of any workarounds for this issue. There
is no configuration option to disable the parsing of Office files in
the browser. Additionally, due to a lack of control over file system
permissions on Apple devices (and the method of library loading) it is
not possible to remove or block access to the OfficeImport binary.

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/HT4435

VII. CVE INFORMATION

The Common Vulnerabilities and Exposures (CVE) project has assigned the
name CVE-2010-3786 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

08/25/2010  Initial Vendor Notification
08/25/2010  Initial Vendor Reply
11/11/2010  Coordinated Public Disclosure

IX. CREDIT

This vulnerability was reported to iDefense by Tobias Klein.

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Copyright © 2010 iDefense, Inc.

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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
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