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- - -----------------------------------------------------------------
Title:  Buffer Overrun in Windows Could Lead to Data 
	Corruption (817606)
Date:       09 July 2003
Software:   
 - Microsoft Windows NT Server 4.0
 - Microsoft Windows NT Server 4.0, Terminal Server Edition 
 - Microsoft Windows 2000
 - Windows XP Professional 
Impact:     Allow an attacker to execute code of their choice
Max Risk:   Important
Bulletin:   MS03-024

Microsoft encourages customers to review the Security Bulletins 
at: http://www.microsoft.com/technet/security/bulletin/MS03-
024.asp
http://www.microsoft.com/security/security_bulletins/ms03-024.asp
- - -----------------------------------------------------------------

Issue:
======
Server Message Block (SMB) is the Internet Standard protocol that
Windows uses to share files, printers, serial ports, and to
communicate between computers using named pipes and mail slots.
In a networked environment, servers make file systems and 
resources available to clients. Clients make SMB requests for 
resources, and servers make SMB responses in what's described as 
a client server request-response protocol. 

A flaw exists in the way that the server validates the parameters
of an SMB packet. When a client system sends an SMB packet to the
server system, it includes specific parameters that provide the
server with a set of "instructions." In this case, the server is
not properly validating the buffer length established by the 
packet. If the client specifies a buffer length that is less than 
what is needed, it can cause the buffer to be overrun. 

By sending a specially crafted SMB packet request, an attacker
could cause a buffer overrun to occur. If exploited, this could
lead to data corruption, system failure, or-in the worst case-
it could allow an attacker to run the code of their choice.
An attacker would need a valid user account and would need to
be authenticated by the server to exploit this flaw.

Mitigating Factors:
====================
 - Windows Server 2003 is not affected by this vulnerability.
 - By default, it is not possible to exploit this flaw 
anonymously. The attacker would have to be authenticated by the 
server prior to attempting to send a SMB packet to it.
 - Blocking port 139/445 at the firewall will prevent the
possibility of an attack from the Internet.

Risk Rating:
============
 - Important

Patch Availability:
===================
 - A patch is available to fix this vulnerability. Please read 
the Security Bulletins at 
http://www.microsoft.com/technet/security/bulletin/ms03-024.asp
http://www.microsoft.com/security/security_bulletins/ms03-024.asp

for information on obtaining this patch.

Acknowledgment:
===============
 - Microsoft thanks  Jeremy Allison and Andrew Tridgell, Samba 
Team for reporting this issue to us and working with us to 
protect customers.
- - -----------------------------------------------------------------

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