iDefense Security Advisory 12.04.08: Sun Java JRE TrueType Font Parsing Integer Overflow Vulnerability

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iDefense Security Advisory 12.02.08
http://labs.idefense.com/intelligence/vulnerabilities/
Dec 02, 2008

I. 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.

II. 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.

III. 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.

IV. 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.

V. 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.

VI. 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

VII. CVE INFORMATION

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

VIII. 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

IX. CREDIT

This vulnerability was reported to iDefense by Sebastian Apelt
([email protected]).

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X. LEGAL NOTICES

Copyright © 2008 iDefense, Inc.

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 [email protected] 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.
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