iDefense Security Advisory 07.20.11 http://labs.idefense.com/intelligence/vulnerabilities/ Jul 20, 2011 I. BACKGROUND WebKit is an open source web browser engine. It is currently used by Apple Inc.'s Safari browser, as well as by Google's Chrome browser. For more information, see the vendor's site at the following link. http://webkit.org/ II. DESCRIPTION Remote exploitation of a use-after-free vulnerability in WebKit, as included with Apple Inc.'s Safari Web browser, could allow an attacker to execute arbitrary code with the privileges of the current user.

The vulnerability occurs during the processing of a malformed TIFF image. Specifically, it is possible to trigger a use-after-free vulnerability when Safari fails to properly release an object. The object's memory is freed; however, a reference to the object remains. When the reference is later used to access the object, this now invalid memory is treated as a valid object and the object's vtable is used to make an indirect function call. This may result in the execution of arbitrary code. III. ANALYSIS Exploitation of this vulnerability results in the execution of arbitrary code with the privileges of the user viewing the Web page. To exploit this vulnerability, a targeted user must load a malicious Web page created by an attacker. An attacker typically accomplishes this via social engineering or injecting content into compromised, trusted sites. After the user visits the malicious Web page, no further user interaction is needed. IV. DETECTION Safari versions prior to 5.1 and 5.0.6 are vulnerable. V. WORKAROUND iDefense is currently unaware of effective workarounds for this vulnerability, as it is not possible to disable TIFF support; however, disabling JavaScript will make it more difficult to exploit the vulnerability. 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/HT4808 VII. CVE INFORMATION The Common Vulnerabilities and Exposures (CVE) project has assigned the name CVE-2011-0215 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 02/02/2011 Initial Vendor Notification 02/02/2011 Initial Vendor Reply 07/20/2011 Coordinated Public Disclosure IX. CREDIT This vulnerability was reported to iDefense by Juan Pablo Lopez Yacubian. Get paid for vulnerability research http://labs.idefense.com/methodology/vulnerability/vcp.php Free tools, research and upcoming events http://labs.idefense.com/ X. LEGAL NOTICES Copyright © 2011 Verisign Permission is granted for the redistribution of this alert electronically. It may not be edited in any way without the express written consent of iDefense. If you wish to reprint the whole or any part of this alert in any other medium other than electronically, please e-mail customerservice@idefense.com for permission. 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.