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Sun Java JRE TrueType Font Parsing Integer Overflow Vulnerability

04.12.08

BACKGROUND

The Sun Java JRE is Sun's implementation of the Java runtime. For more information, see the vendor's site found at the following link.

DESCRIPTION

Remote exploitation of an integer overflow vulnerability in Sun Microsystems Inc.'s Java JRE could allow an attacker to execute arbitrary code with the privileges of the current user.

The vulnerability exists within the font parsing code in the JRE. As part of its font API, the JRE provides the ability to load a font from a remote URL. Various types of fonts are supported, one of which is the TrueType format font. The vulnerability occurs when parsing various structures in TrueType font files. During parsing, values are taken from the file, and without being properly validated, used in operations that calculate the number of bytes to allocate for heap buffers. The calculations can overflow, resulting in a potentially exploitable heap overflow.

ANALYSIS

Exploitation allows attackers to execute arbitrary code in the context of the currently logged on user. 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.

DETECTION

iDefense has confirmed the existence of this vulnerability in Sun Microsystem Inc.'s Java JRE version 1.6.0_05 for Windows. Previous versions may also be affected.

WORKAROUND

There is a potential workaround for the vulnerability, but it renders the JRE unusable. It is possible to use the cacls program to change the file permissions on fontmanager.dll. This will prevent the vulnerable library from loading. However, this workaround has a serious impact on the functionality of the JRE. When a webpage attempts to load an applet, the JRE will abort with a runtime error, and the browser will close.

VENDOR RESPONSE

Sun Microsystem Inc. has released a patch which addresses this issue. For more information, consult their advisory at the following URL.

http://sunsolve.sun.com/search/document.do?assetkey=1-66-244987-1

CVE INFORMATION

A Mitre Corp. Common Vulnerabilities and Exposures (CVE) number has not been assigned yet.

DISCLOSURE TIMELINE

07/31/2008 Initial Vendor Notification
08/01/2008 Initial Vendor Reply
10/21/2008 Additional Vendor Feedback
11/26/2008 Additional Vendor Feedback
12/02/2008 Coordinated Public Disclosure

CREDIT

This vulnerability was reported to iDefense by Sebastian Apelt (webmaster@buzzworld.org).

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LEGAL NOTICES

Copyright © 2008 Verisign, Inc.

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