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Apple Mobile OfficeImport Framework Excel Parsing Memory Corruption Vulnerability

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/

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.

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.

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.

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.

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

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.

DISCLOSURE TIMELINE

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

CREDIT

This vulnerability was reported to iDefense by Tobias Klein.

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LEGAL NOTICES

Copyright © 2010 Verisign, 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 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.