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             AUSCERT External Security Bulletin Redistribution

           ESB-2003.0278 -- Microsoft Security Bulletin MS03-012
  Flaw In Winsock Proxy Service And ISA Server Firewall Service Can Cause
                        Denial Of Service (331066)
                               11 April 2003

===========================================================================

        AusCERT Security Bulletin Summary
        ---------------------------------

Product:                Proxy Server 2.0
                        ISA Server 2000
Vendor:                 Microsoft
Operating System:       Windows
Impact:                 Denial of Service
Access Required:        Remote
CVE Names:              CAN-2003-0110

Ref:                    ESB-2003.0273

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Title:      Flaw In Winsock Proxy Service And ISA Firewall Service 
	    Can Cause Denial Of Service (331066)
Date:       09 April 2003
Software:   Microsoft Proxy Server 2.0, Microsoft ISA Server 
Impact:     denial of service
Max Risk:   Important
Bulletin:   MS03-012

Microsoft encourages customers to review the Security Bulletins 
at: 

http://www.microsoft.com/technet/security/bulletin/MS03-012.asp
http://www.microsoft.com/security/security_bulletins/ms03-012.asp
- - -------------------------------------------------------------------


Issue:
======
There is a flaw in the Winsock Proxy service in Microsoft Proxy 
Server 2.0, and the Microsoft Firewall service in ISA Server 2000, 
that would allow an attacker on the internal network to send a 
specially crafted packet that would cause the server to stop 
responding to internal and external requests. Receipt of such a 
packet would cause CPU utilization on the server to reach 100%, and 
thus make the server unresponsive. The Winsock Proxy service and 
Microsoft Firewall service work with FTP, telnet, mail, news, 
Internet Relay Chat (IRC), or other client applications that are 
compatible with Windows Sockets (Winsock). These services allow 
these applications to perform as if they were directly connected to 
the Internet. These services redirect the necessary communications 
functions to a Proxy Server 2.0 or ISA Server computer, thus 
establishing a communication path from the internal application to 
the Internet through it. 

Mitigating Factors:
====================

- - - The vulnerability would not enable an attacker to gain any 
privileges on an affected Proxy Server 2.0 or ISA Server computer 
or compromise any cached content. It is strictly a denial of 
service.
 
- - - ISA Server computers running in cache mode are not affected 
because the Microsoft Firewall service is disabled by default. 


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/ms03-012.asp
http://www.microsoft.com/security/security_bulletins/ms03-12.asp

for information on obtaining this patch.

- - ----------------------------------------------------------------

THE INFORMATION PROVIDED IN THE MICROSOFT KNOWLEDGE BASE IS 
PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND. MICROSOFT 
DISCLAIMS ALL WARRANTIES, EITHER EXPRESS OR IMPLIED, INCLUDING 
THE WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 
PURPOSE. IN NO EVENT SHALL MICROSOFT CORPORATION OR ITS 
SUPPLIERS BE LIABLE FOR ANY DAMAGES WHATSOEVER INCLUDING DIRECT, 
INDIRECT, INCIDENTAL, CONSEQUENTIAL, LOSS OF BUSINESS PROFITS OR 
SPECIAL DAMAGES, EVEN IF MICROSOFT CORPORATION OR ITS SUPPLIERS 
HAVE BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES. SOME 
STATES DO NOT ALLOW THE EXCLUSION OR LIMITATION OF LIABILITY FOR 
CONSEQUENTIAL OR INCIDENTAL DAMAGES SO THE FOREGOING LIMITATION 
MAY NOT APPLY.

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