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A  U  S  C  E  R  T                                           A  L  E  R  T

                        AL-2003.08 -- AUSCERT ALERT
Unchecked Buffer In Windows Component Could Cause Server Compromise (815021)
               Microsoft Security Bulletin MS03-007 REVISED
                                29 May 2003
===========================================================================

        AusCERT Alert Summary
        ---------------------

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

Ref:                    AU-2003.006
                        AL-2003.02
                        ESB-2003.0313
                        ESB-2003.0182

Due to the severity and current exploitation of this vulnerability
against Windows 2000 servers, and now that the vulnerability has been
found to exist in Windows NT 4.0 and Windows XP, AusCERT is releasing
this information as an AusCERT Alert.

For additional information and appropriate patches, please reference
the Microsoft Security Bulletin MS03-007, available at:

 http://www.microsoft.com/technet/security/bulletin/ms03-007.asp

AusCERT will continue to monitor this vulnerability and any exploit
activity. AusCERT members will be updated as information becomes
available.

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- - - -----------------------------------------------------------------
Title:      Unchecked Buffer In Windows Component Could Cause 
            Server Compromise (815021)
Released:   17 Mar 2003
Revised:    28 May 2003 (version 3.0)
Software:   Microsoft (r) Windows (r) NT 4.0, Windows 2000 and    
            Windows XP
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. During the course of that investigation, 
Microsoft found that 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. In addition, Microsoft has recently been made aware of this 
vulnerability as well in Windows XP. However, like Windows NT 4.0, 
Windows XP does not install Internet Information Services (IIS) by 
default. Microsoft has now released patches for Windows NT 4.0 and 
Windows XP.

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 
 - Windows NT 4.0 and Windows XP do not install Internet 
Information Services by default. 
 - Windows NT 4.0 does not support WebDAV 


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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This alert is provided as a service to AusCERT's members.  As AusCERT did
not write the document quoted above, AusCERT has had no control over its   
content.  The decision to use any or all of this information is the
responsibility of each user or organisation, and should be done so in
accordance with site policies and procedures.

NOTE: This is only the original release of the alert.  It may not be
updated when updates to the original are made.  If downloading at a later
date, it is recommended that the alert is retrieved directly from the
author's website to ensure that the information is still current.

Contact information for the authors of the original document is included
in the alert above.  If you have any questions or need further information,
please contact them directly.

Previous advisories, alerts and external security bulletins can be 
retrieved from:

        http://www.auscert.org.au/render.html?cid=1977

If you believe that your system has been compromised, contact AusCERT or
your representative in FIRST (Forum of Incident Response and Security
Teams).

Internet Email: auscert@auscert.org.au
Facsimile:      (07) 3365 7031
Telephone:      (07) 3365 4417 (International: +61 7 3365 4417)
                AusCERT personnel answer during Queensland business
                hours which are GMT+10:00 (AEST).  On call after hours
                for member emergencies only.

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