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Q286818: IIS: Malformed URL Cause Service Failure in IIS 5.0 & Exch 2000

Article: Q286818
Product(s): Internet Information Server
Version(s): 5.0
Operating System(s): 
Keyword(s): kbWin2000PreSP2Fix kbWin2000SP2Fix kbgraphxlinkcritical
Last Modified: 08-MAY-2002

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The information in this article applies to:

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

Microsoft Internet Information Services (IIS) 5.0 contains a flaw that affects
the way that a URL is handled if it has a specific construction and its length
is within a very narrow range of values. If such a URL were repeatedly sent to
an affected system, a confluence of events could cause a memory allocation error
that would result in the failure of the IIS service.

IIS 5.0 is affected by the same vulnerability as the Microsoft Exchange 2000
Server vulnerability that is described in the following article in the Microsoft
Knowledge Base:

  Q287678 XWEB: Malformed URL Can Cause Service Failure in IIS 5.0 and Exchange
  2000 Server

Mitigating factors:

- The vulnerability would not enable the attacker to gain any administrative
  control over the server or to alter any data on it.

- The affected services automatically restart in the event of a failure;
  therefore, an affected system would resume service almost immediately.

- A successful attack against an Exchange server would only disrupt Web-based
  mail clients' use of the server. The server would continue to be available
  for MAPI-based clients such as Microsoft Outlook.

- The ISAPI involved in this vulnerability authenticates the user before
  servicing the request; therefore, a properly configured Exchange server would
  be at less risk than an IIS server.

RESOLUTION
==========

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

  Q260910 How to Obtain the Latest Windows 2000 Service Pack

IMPORTANT: Because the flaw occurs in two different code modules, one of which is
installed as part of IIS 5.0 and both of which are installed as part of Exchange
2000, it is important for Exchange 2000 administrators to install both the IIS
and Exchange patches below.

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

  IIS 5.0:
  DownloadDownload Q286818_W2K_SP3_x86_en.exe now
  (http://www.microsoft.com/Downloads/Release.asp?ReleaseID=28155)

  Exchange 2000 Server:
  DownloadDownload Q287678engi386.exe now
  (http://www.microsoft.com/Downloads/Release.asp?ReleaseID=28369)

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

  Q119591 How to Obtain Microsoft Support Files from Online Services

Microsoft used the most current virus detection software available on the date of
posting to scan this file for viruses. After it is posted, the file is housed 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
  -----------------------------------------------------
  02/01/2001  07:21p  0.9.3940.16  428,816  Httpext.dll


STATUS
======

Microsoft has confirmed this to be a problem in Microsoft Internet Information
Services 5.0. This problem was first corrected in Windows 2000 Service Pack 2.

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 about this issue, see the following Microsoft Web site:

  http://www.microsoft.com/technet/security/bulletin/ms01-014.asp

For additional information about how to install Microsoft Windows 2000 and
Microsoft Windows 2000 hotfixes at the same time, click the article number below
to view the article in the Microsoft Knowledge Base:

  Q249149 Installing Microsoft Windows 2000 and Windows 2000 Hotfixes

Additional query words: dos denial of service security_patch

======================================================================
Keywords          : kbWin2000PreSP2Fix kbWin2000SP2Fix kbgraphxlinkcritical 
Technology        : kbiisSearch kbiis500
Version           : :5.0
Hardware          : x86
Issue type        : kbbug
Solution Type     : kbfix

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

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