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CERT Advisory CA-2002-33 Heap Overflow Vulnerability in Microsoft Data
Access Components (MDAC)

   Original release date: November 21, 2002
   Last revised: --
   Source: CERT/CC

   A complete revision history can be found at the end of this file.

Systems Affected

   All Microsoft Windows systems running the following:
     * Versions of Microsoft Data Access Components (MDAC) prior to 2.7
     * Internet Explorer version 6
     * Internet Explorer version 5.5
     * Internet Explorer version 5.1

   Note that Microsoft Windows XP is shipped with MDAC version 2.7 and is
   not  vulnerable  by  default  even  though  Internet  Explorer  6.0 is
   installed.

   Because  the  normal operation of several applications and web servers
   on  a  system  depend  on  the  proper  operation  of the MDAC ActiveX
   control,  other  programs  could  be  used  as  an exploit vector. For
   example, Internet Information Server may be configured to use MDAC.

Overview

   A  vulnerability  in the Microsoft Data Access Components (MDAC) could
   lead  to  remote  execution of code with the privileges of the current
   process or user.

I. Description

   Microsoft  Data  Access Components (MDAC) is a collection of utilities
   and  routines  to  process  requests  between  databases  and  network
   applications.  A  buffer  overflow  vulnerability exists in the Remote
   Data Services (RDS) component of MDAC.

   The RDS component provides an intermediary step for a client's request
   for  service  from  a  back-end  database that enables the web site to
   apply business logic to the request.

   According  to Microsoft's Security Bulletin MS02-065, a routine in the
   RDS  component,  specifically  the RDS Data Stub function, contains an
   unchecked  buffer.  The  RDS  Data Stub function's purpose is to parse
   incoming  HTTP  requests  and  generate  RDS  commands. This unchecked
   buffer could be exploited to cause a heap overflow.

   There  are  two ways in which this vulnerability can be exploited. The
   first  involves  an  attacker  sending  a  malicious HTTP request to a
   vulnerable  service,  such  as  an  IIS server. If RDS is enabled, the
   attacker  can  execute  arbitrary  code  as the IIS server. RDS is not
   enabled  by  default on Windows 2000 and Windows XP systems. It can be
   disabled  on  other  systems  by  following  the advice in Microsoft's
   security bulletin.

   The  other  way to exploit this vulnerability involves a malicious web
   site  hosting a page that exploits the buffer overflow in the MDAC RDS
   stub  through  a  client  application, such as Internet Explorer. Most
   systems  running  Internet  Explorer  on  operating systems other than
   Windows  XP are vulnerable to this attack. The attacker is able to run
   arbitrary code as the user viewing the malicious web page.

   Both  web  servers  and  client  applications  that  rely  on MDAC are
   affected.  It  is  recommended that all users of Microsoft Windows 98,
   Windows  98 SE, Windows ME, Windows NT 4.0, and Windows 2000 apply the
   patch (Q329414). Windows XP users are not affected since MDAC 2.7, the
   non-vulnerable version, is installed by default.

   Information  about  this vulnerability is discussed in VU#542081. This
   issue is also being referenced as CAN-2002-1142.

II. Impact

   A  remote attacker could execute arbitrary code with the privileges of
   the application that processed the request.

   In the case of a web server or other service, this is likely to be the
   SYSTEM  or  another account with elevated privileges. In the case of a
   client  application,  this  will  be  the account used to view the web
   page.

III. Solution

 Apply a patch from your vendor.

   Microsoft  has  released  a  patch  (Q329414)  and a security bulletin
   (MS02-065)  to  address this issue. An end-user version of MS02-065 is
   available at
   http://www.microsoft.com/security/security_bulletins/ms02-065.asp.

   According  to  the Microsoft advisory, a scenario exists in by which a
   vulnerable  version  of  the  control may be re-installed on a Windows
   system  even after the patch has been applied. This is due to the fact
   that  the  vulnerable  ActiveX  control is signed by Microsoft and the
   patch does not set the kill bit for the MDAC control.
   _________________________________________________________________

   This  vulnerability  was  reported in an advisory by Foundstone and in
   MS02-065 by Microsoft.
   _________________________________________________________________

   Feedback  can  be  sent  to  the  Authors:  Jason  A.  Rafail, Chad R.
   Dougherty, and Cory F. Cohen.
   ______________________________________________________________________

   This document is available from:
   http://www.cert.org/advisories/CA-2002-33.html
   ______________________________________________________________________

CERT/CC Contact Information

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          Phone: +1 412-268-7090 (24-hour hotline)
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   Copyright 2002 Carnegie Mellon University.

   Revision History
     November 21, 2002: Initial release

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