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===========================================================================
             AUSCERT External Security Bulletin Redistribution

           ESB-2003.0313 -- Microsoft Security Bulletin MS03-007
    Unchecked Buffer In Windows Component Could Cause Server Compromise
                                 (815021)
                               28 April 2003

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

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

Product:                Windows ntdll.dll
Vendor:                 Microsoft
Operating System:       Windows 2000
                        Windows NT
Impact:                 Administrator Compromise
Access Required:        Remote
CVE Names:              CAN-2003-0109

Ref:                    AL-2003.02
                        ESB-2003.0182

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Title:      Unchecked Buffer In Windows Component Could Cause        
   
Server Compromise (815021)
Released:   17 Mar 2003
Revised:    23 Apr 2003 (version 2.0)
Software:   Microsoft (r) Windows (r) NT 4.0 and Windows 2000
Impact:     Run code of attacker's choice
Max Risk:   Critical
Bulletin:   MS03-007

Microsoft encourages customers to review the Security Bulletin 
at: http://www.microsoft.com/technet/security/bulletin/MS03-007.asp
http://www.microsoft.com/security/security_bulletins/ms03-007.asp
- - ----------------------------------------------------------------------

Reason for Revision:
====================
Microsoft originally released this security bulletin on March 17, 
2003. At that time, Microsoft was aware of a publicly available 
exploit that was being used to attack Windows 2000 Servers 
running IIS 5.0. The attack vector in this case was WebDAV 
although the underlying vulnerability was in a core operating 
system component, ntdll.dll. Microsoft issued a patch to protect 
Windows 2000 customers shortly afterwards, but also continued to 
investigate the underlying vulnerability. Windows NT 4.0 also 
contains the underlying vulnerability in ntdll.dll, however it 
does not support WebDAV and therefore the known exploit was not 
effective against Windows NT 4.0. Microsoft has now released a 
patch for Windows NT 4.0.

Issue:
======
Microsoft Windows 2000 supports the World Wide Web Distributed 
Authoring and Versioning (WebDAV) protocol. WebDAV, defined in 
RFC 2518, is a set of extensions to the Hyper Text Transfer 
Protocol (HTTP) that provide a standard for editing and file 
management between computers on the Internet. A security 
vulnerability is present in a Windows component used by WebDAV 
and results because a core operating system component, ntdll.dll, 
contains an unchecked buffer. 

An attacker could exploit the vulnerability by sending a 
specially formed HTTP request to a machine running Internet 
Information Server (IIS). The request could cause the server to 
fail or to execute code of the attacker's choice. The code would 
run in the security context of the IIS service (which, by 
default, runs in the LocalSystem context). 

Although Microsoft has supplied a patch for this vulnerability 
and recommends all affected customers install the patch 
immediately, additional tools and preventive measures have been 
provided that customers can use to block the exploitation of 
this vulnerability while they are assessing the impact and 
compatibility of the patch. These temporary workarounds and 
tools are discussed in the "Workarounds" section in the FAQ 
below.

Mitigating Factors:
====================
- - -URLScan, which is a part of the IIS Lockdown Tool will block 
this attack in its default configuration.

- - -The vulnerability can only be exploited remotely if an attacker 
can establish a web session with an affected server.

Risk Rating:
============
 - Critical

Patch Availability:
===================
 - A patch is available to fix this vulnerability. Please read the 
   Security Bulletins at
   http://www.microsoft.com/technet/security/bulletin/ms03-007.asp
   http://www.microsoft.com/security/security_bulletins/ms03-007.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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