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ISS Security Brief: Microsoft ASN.1 Integer Manipulation vulns
ISS Security Brief: Microsoft ASN.1 Integer Manipulation Vulnerabilities


Internet Security Systems Security Brief
February 11, 2004

Microsoft ASN.1 Integer Manipulation Vulnerabilities


Microsoft has release Security Bulletin MS04-007 to address vulnerabilities 
in the ASN.1 parsing component of the Windows Operating Systems. This 
component is used by several applications for transmission of data across 
the network. Some examples of applications which make use of ASN.1 include 
Internet Explorer and IIS for certificate parsing, NTLMv2 authentication, 
Kerberos authentication, ISAKMP, LDAP and Exchange.


The vulnerability could be exploited by remote attackers to cause a Denial 
of Service (DoS) or potentially gain access to a vulnerable machine with 
the privileges of the services being exploited. This vulnerability may be 
exploited in many default configurations if vulnerable services are remotely 

There are currently no known exploits in the wild for this issue. Due to 
the nature of this vulnerability, reliable and successful remote 
exploitation is considered difficult.

Known Affected Products:

Microsoft Windows NT4, 2000, XP and 2003 when used with one of the 
following applications:

- - NTLMv2 authentication
- - Internet Explorer
- - Outlook
- - IIS 4.0, 5.0, 5.1 and 6.0 with client certificate parsing enabled
- - Exchange 5.x, 2000, 2003
- - LDAP
- - Kerberos

For complete ISS X-Force Security Alert, please visit: 


About Internet Security Systems (ISS) 
Founded in 1994, Internet Security Systems (ISS) (Nasdaq: ISSX) is a 
pioneer and world leader in software and services that protect critical 
online resources from an ever-changing spectrum of threats and misuse. 
Internet Security Systems is headquartered in Atlanta, GA, with 
additional operations throughout the Americas, Asia, Australia, Europe 
and the Middle East. 

Copyright (c) 2003 Internet Security Systems, Inc. All rights reserved 

Permission is hereby granted for the electronic redistribution of this 
document. It is not to be edited or altered in any way without the 
express written consent of the Internet Security Systems X-Force. If 
you wish to reprint the whole or any part of this document in any other 
medium excluding electronic media, please email for 

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 otherwise, with regard to 
this information or its use. Any use of this information is at the 
user's risk. In no event shall the author/distributor (Internet Security 
Systems X-Force) be held liable for any damages whatsoever arising out 
of or in connection with the use or spread of this information. 

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