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

           ESB-2002.279 -- Microsoft Security Bulletin MS02-029
            Unchecked Buffer in Remote Access Service Phonebook
                  Could Lead to Code Execution (Q318138)
                               13 June 2002

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

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

Product:                Routing and Remote Access Server (RRAS)
Vendor:                 Microsoft
Operating System:       Windows NT 4.0
                        Windows NT 4.0 Terminal Server
                        Windows 2000
                        Windows XP
Impact:                 Denial of Service
                        Execute Arbitrary Code/Commands
Access Required:        Existing Account

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Title:      Unchecked Buffer in Remote Access Service Phonebook Could
            Lead to Code Execution (Q318138)
Date:       12 June 2002
Software:   Windows NT 4.0, NT 4.0 Terminal Server Edition, 2000, XP,
            Routing and Remote Access Server (RRAS)
Impact:     Local Privilege Escalation
Max Risk:   Critical
Bulletin:   MS02-029

Microsoft encourages customers to review the Security Bulletin at:
http://www.microsoft.com/technet/security/bulletin/MS02-029.asp.
- - ----------------------------------------------------------------------

Issue:
======
The Remote Access Service (RAS) provides dial-up connections between 
computers and networks over phone lines. RAS is delivered as a native
system service in Windows NT 4.0, Windows 2000 and Windows XP, and 
also is included in a separately downloadable Routing and Remote 
Access Server (RRAS) for Windows NT 4.0. All of these implementations
include a RAS phonebook, which is used to store information about 
telephone numbers, security, and network settings used to dial-up 
remote systems. 

A flaw exists in the RAS phonebook implementation: a phonebook value 
is not properly checked, and is susceptible to a buffer overrun. The 
overrun could be exploited for either of two purposes: causing a 
system failure, or running code on the system with LocalSystem 
privileges. If an attacker were able to log onto an affected server
and modify a phonebook entry using specially malformed data, then 
made a connection using the modified phonebook entry, the specially 
malformed data could be run as code by the system. 


Mitigating Factors:
====================
 - The vulnerability could only be exploited by an attacker who had 
   the appropriate credentials to log onto an affected system. 

 - Best practices suggests that unprivileged users not be allowed to 
   interactively log onto business-critical servers. If this 
   recommendation has been followed machines such as domain  
   controllers, ERP servers, print and file servers, database 
   servers, and others would not be at risk from this vulnerability.
   

Risk Rating:
============
 - Internet systems: Low
 - Intranet systems: Critical
 - Client systems: Moderate

Patch Availability:
===================
 - A patch is available to fix this vulnerability. Please read the
   Security Bulletin at
   http://www.microsoft.com/technet/security/bulletin/ms02-029.asp
   for information on obtaining this patch.

Acknowledgment:
===============
 - David Litchfield of Next Generation Security Software Ltd.
   (http://www.nextgenss.com/)

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

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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