Q318091: MS02-018: Patch for Buffer Overrun in HTR ISAPI Extension

Article: Q318091
Product(s): Internet Information Server
Version(s): 4.0,5.0
Operating System(s): 
Keyword(s): kbSecurity kbCOMIS kbWinNT400PreSP7Fix kbWin2000PreSP3Fix kbWin2000sp3fix
Last Modified: 15-AUG-2002

-------------------------------------------------------------------------------
The information in this article applies to:

- Microsoft Internet Information Services version 5.0 
- Microsoft Internet Information Server version 4.0 
-------------------------------------------------------------------------------

SYMPTOMS
========

A buffer overrun vulnerability exists in Internet Information Server (IIS) 4.0
and Internet Information Services (IIS) 5.0. By sending a specially chosen
request to an affected Web server, an attacker can cause the server to
temporarily stop providing Web services or, in very unusual cases, the attacker
can gain control of the server.

A number of factors, including the following, tend to reduce the severity of this
vulnerability:

- It is extremely hard to inject code by exploiting this vulnerability because
  the overrun is not on the stack and is only a single byte over the allocated
  buffer.

- By default, the IIS Lockdown Tool removes the component that contains the
  vulnerability.

- The default configuration of the URLScan tool prevents the vulnerability from
  being exploited.

CAUSE
=====

This vulnerability occurs because the Internet Server Application Programming
Interface (ISAPI) extension that implements HTR scripting contains an off-by-one
error when it calculates the size of a buffer for storing an input value. If a
request for an HTR script is malformed in a particular way, it is possible to
abuse the miscalculation and conduct a buffer overrun attack. In the least
serious case, this can result in the failure of the IIS service; in the most
serious case (which is very hard to exploit), it can allow code to be run on the
server.

RESOLUTION
==========

- Internet Information Services 5.0
- Internet Information Server 4.0

Internet Information Services 5.0
---------------------------------

The update for this problem is included in the "MS02-018: April 2002 Cumulative
Patch for Internet Information Services". For additional information about how
to obtain this patch, click the article number below to view the article in the
Microsoft Knowledge Base:

  Q319733 MS02-018: April 2002 Cumulative Patch for Internet Information
  Services

To resolve this problem, obtain the latest service pack for Windows 2000. For
additional information, click the following article number to view the article
in the Microsoft Knowledge Base:

  Q260910 How to Obtain the Latest Windows 2000 Service Pack

Internet Information Server 4.0
-------------------------------

The update for this problem is included in the "MS02-018: April 2002 Cumulative
Patch for Internet Information Services". For additional information about how
to obtain this patch, click the article number below to view the article in the
Microsoft Knowledge Base:

  Q319733 MS02-018: April 2002 Cumulative Patch for Internet Information
  Services

STATUS
======

Internet Information Services 5.0
---------------------------------

Microsoft has confirmed that this problem may cause a degree of security
vulnerability in Microsoft Internet Information Services 5.0. This problem was
first corrected in Windows 2000 Service Pack 3.

Internet Information Server 4.0
-------------------------------

Microsoft has confirmed that this problem may cause a degree of security
vulnerability in Microsoft Internet Information Server 4.0.

MORE INFORMATION
================

For more information on these vulnerabilities, see the following Microsoft Web
site:

  http://www.microsoft.com/technet/security/bulletin/MS02-018.asp

For additional information about how to obtain a hotfix for Windows 2000
Datacenter Server, click the article number below to view the article in the
Microsoft Knowledge Base:

  Q265173 Datacenter Program and Windows 2000 Datacenter Server Product

For additional information on how to install multiple hotfixes with only one
reboot, click the article number below to view the article in the Microsoft
Knowledge Base:

  Q296861 Use QChain.exe to Install Multiple Hotfixes with One Reboot

Additional query words: kbIISCom kbIIS400500510April2002Rollup security_patch

======================================================================
Keywords          : kbSecurity kbCOMIS kbWinNT400PreSP7Fix kbWin2000PreSP3Fix kbWin2000sp3fix 
Technology        : kbiisSearch kbiis500 kbiis400
Version           : :4.0,5.0
Hardware          : x86
Issue type        : kbbug
Solution Type     : kbfix

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

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.

Copyright Microsoft Corporation 1986-2002.