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[EEYEB-2000801] - Windows Embedded Open Type (EOT) Font Heap Overflow Vulnerability
From: "Advisories" <Advisories () eeye com>
Date: Tue, 10 Jan 2006 12:09:36 -0800

EEYEB-20050801 Windows Embedded Open Type (EOT) Font Heap Overflow
Vulnerability

Release Date:
January 10, 2006

Date Reported:
July 31, 2005

Time to Patch:
163 Days

Severity:
High (Code Execution)

Systems Affected:
Windows ME
Windows 98
Windows NT
Windows 2000
Windows XP SP1 / SP2
Windows Server 2003 SP0 / SP1

Overview:
eEye Digital Security has discovered a vulnerability in the way Windows
uncompresses Embedded Open Type fonts that would allow the author of a
malicious web page to execute arbitrary code on the system of a user who
visits the site, at the privilege level of that user.

Embedded Open Type fonts are referenced through the use of style data,
as the following snippet illustrates:

    @font-face {
        font-family: Abysmal;
        font-style:  normal;
        font-weight: normal;
        src: url(evil.eot);

Although these fonts typically have .eot file extensions, it should be
noted that any extension may be used in order to exploit this
vulnerability.

Technical Details:
A heap overflow vulnerability exists in T2EMBED.DLL, which Internet
Explorer invokes to process EOT fonts.  The data within an EOT file is
compressed in Agfa MicroType Express format, which hosts an
LZ-compressed stream that includes a 24-bit allocation size.  This size
+ 1C00h is allocated within the function MTX_LZCOMP_UnPackMemory, but
the resulting allocation size is not validated before data is copied
into the block, allowing a malformed EOT file to cause an essentially
arbitrary-length heap buffer overflow with binary data.

Protection:
Retina Network Security Scanner has been updated to identify this
vulnerability.
Blink End-Point Protection proactively protects against this
vulnerability.

Vendor Status:
Microsoft has released a patch for this vulnerability.  The patch is
available at:
http://www.microsoft.com/technet/security/bulletin/MS06-002.mspx

References:
EEYE ID# EEYEB-20050801
OSVDB ID# 18829
CVE # CVE-2006-0010

Credit:
Fang Xing

Greetings:
eEye Research and especially Derek for all his help

Copyright (c) 1998-2006 eEye Digital Security Permission is hereby
granted for the redistribution of this alert electronically.  It is not
to be edited in any way without express consent of eEye.  If you wish to
reprint the whole or any part of this alert in any other medium
excluding electronic medium, please email alert () eEye com for permission.

Disclaimer:
The information within this paper may change without notice.  Use of
this information constitutes acceptance for use in an AS IS condition.
There are no warranties, implied or express, with regard to this
information.  In no event shall the author be liable for any direct or
indirect damages whatsoever arising out of or in connection with the use
or spread of this information.  Any use of this information is at the
user's own risk.
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