NSFOCUS Security Advisory (SA2007-01)

Microsoft IE5 CSS Parsing Memory Corruption Vulnerability

Release Date: 2007-08-15

CVE ID: CVE-2007-0943

http://www.nsfocus.com/english/homepage/research/0701.htm

Affected systems & software
===================

Internet Explorer 5.01


Unaffected systems & software
===================


Summary
=========

NSFocus Security Team discovered a memory corruption vulnerability in IE 5 
that allows arbitrary code execution when parsing a malicious CSS file.

Description
============

There exists a vulnerability when IE 5.0 parses CSS due to insufficient check 
on the pointer. Out-of-bound pointer reference and memory overwriting might 
occur in the handling of malformed CSS files, which allows attackers to run 
arbitrary code via carefully crafted  data. 

Attackers can run arbitrary code by crafting a malicious WEB page and alluring 
users to visit it. If the victim is an administrator, then attackers can gain 
complete control over the system. 

The system will be vulnerable even if the security level of IE is set to "High". 

Workaround
=============

Do not visit untrusted websites. 
    
Vendor Status
==============

2006.08.31  Informed the vendor
2006.09.01  Vendor confirmed the vulnerability
2007.08.14  Microsoft released MS07-045 to fix the vulnerability.
            
For more details about Microsoft Security Bulletin, please refer to:
http://www.microsoft.com/technet/security/bulletin/MS07-045.mspx

Additional Information
========================

The Common Vulnerabilities and Exposures (CVE) project has assigned the
name CVE-2007-0943 to this issue. This is a candidate for inclusion in the 
CVE list (http://cve.mitre.org), which standardizes names for security problems.
Candidates may change significantly before they become official CVE entries.

Acknowledgment
===============

Hu Qianwei of NSFocus Security Team found the vulnerability.

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==========
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NSFocus Security Team <security@nsfocus.com>
NSFOCUS INFORMATION TECHNOLOGY CO.,LTD
(http://www.nsfocus.com)