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Q285985: New Variant of File Fragment Reading via .HTR Vulnerability

Article: Q285985
Product(s): Internet Information Server
Version(s): 4.0,5.0
Operating System(s): 
Keyword(s): kbSecurity kbCOMIS kbWinNT400PreSP7Fix kbWin2000PreSP3Fix kbgraphxlinkcritical KbSECVul
Last Modified: 15-AUG-2002

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The information in this article applies to:

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

Microsoft has released a patch that eliminates a security vulnerability in
Internet Information Server (IIS) 4.0 and Internet Information Services (IIS)
5.0. Under very unusual conditions, this vulnerability can allow an attacker to
read fragments of files from a Web server.

This vulnerability involves a new variant of the "File Fragment Reading via .HTR"
vulnerability, which is described in Microsoft Security Bulletin (MS00-044)
(http://www.microsoft.com/technet/security/bulletin/ms00-044.asp). Like the
other variants, this one may allow an attacker to request a file in a way that
causes it to be processed by the .htr ISAPI extension. The result of this is
that fragments of server-side files such as .asp files may potentially be sent
to the attacker. There is no capability through this vulnerability to add,
change, or delete files on the server, or to access a file without permissions.

There are a number of significant restrictions on this vulnerability:

- During normal .htr processing, the effect is to strip out the very data that
  would be the most likely to contain sensitive information.

- There must be zeros fortuitously located in the server memory in order for
  the file fragments to be sent.

- If best practices have been followed regarding the need to avoid ever storing
  sensitive information in .asp and other server-side files, there should be no
  sensitive information in the files to begin with.

Customers who have previously disabled the .htr functionality are not affected by
this vulnerability. Microsoft recommends that all customers disable .htr
functionality, unless there is a business-critical reason for keeping it. For
the latter group of customers, a patch is available that eliminates this
vulnerability.

RESOLUTION
==========

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

To resolve this problem, either obtain the hotfix referenced in this section or
Windows 2000 Security Rollup Package 1 (SRP1). For additional information about
SRP1, click the article number below to view the article in the Microsoft
Knowledge Base:

  Q311401 Windows 2000 Security Rollup Package 1 (SRP1), January 2002

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

The following files are available for download from the Microsoft Download
Center:

  DownloadDownload Q285985_w2k_sp3_x86_en.exe now

For additional information about how to download Microsoft Support files, click
the following article number to view the article in the Microsoft Knowledge
Base:

  Q119591 How to Obtain Microsoft Support Files from Online Services

Microsoft scanned this file for viruses. Microsoft used the most current
virus-detection software that was available on the date that the file was
posted. The file is stored on secure servers that prevent any unauthorized
changes to the file.

The English version of this fix should have the following file attributes or
later:

  Date        Time    Version         Size     File name   Platform
  -----------------------------------------------------------------
  5/31/2001   03:31p  5.0.2195.3649  46,352    Ism.dll     x86

NOTE: Due to file dependencies, this hotfix requires Microsoft Windows NT 4.0
Service Pack 5 or Service Pack 6a.


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

Windows NT 4.0:

To resolve this problem, obtain the Windows NT 4.0 Security Rollup Package. For
additional information, click the article number below to view the article in
the Microsoft Knowledge Base:

  Q299444 Post-Windows NT 4.0 Service Pack 6a Security Rollup Package (SRP)

Microsoft Windows NT Server version 4.0, Terminal Server Edition:

To resolve this problem, obtain the Windows NT Server 4.0, Terminal Server
Edition, Security Rollup Package (SRP). For additional information about the
SRP, click the article number below to view the article in the Microsoft
Knowledge Base:

  Q317636 Windows NT Server 4.0, Terminal Server Edition, Security Rollup
  Package

STATUS
======

Microsoft has confirmed that this problem may cause a degree of security
vulnerability in IIS 4.0 and 5.0. This problem was first corrected in Windows
2000 Service Pack 3.

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

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 The Datacenter Program and Windows 2000 Datacenter Server Product

For additional information about 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

For more information on this security vulnerability, please see the following
Microsoft Web site:

  http://www.microsoft.com/technet/security/bulletin/ms01-004.asp

Additional query words: kbIISCom security_patch kbWin2000srp1

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

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

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