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Q246401: MS99-061: IIS May Improperly Parse Specific Escape Characters

Article: Q246401
Product(s): Internet Information Server
Version(s): 3.0,4.0,4.0 SP3,4.0 SP4,4.0 SP5,4.0 SP6
Operating System(s): 
Keyword(s): kbSecurity kbOSWinNT400sp4 kbiis400 kbOSWinNT400sp6 kbWinNT400PreSP7Fix
Last Modified: 16-MAY-2002

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The information in this article applies to:

- Microsoft Internet Information Server version 4.0 
- Microsoft Site Server version 3.0 
- Microsoft Windows NT Server versions 4.0 SP3, 4.0 SP4, 4.0 SP5, 4.0 SP6 
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SYMPTOMS
========

RFC 1738 specifies that Web Servers should allow hexadecimal digits to be input
in URLs by preceding them with the so-called "escape" character, a percent
sign.

Microsoft Internet Information Server (IIS) complies with the RFC 1738
specification, but also accepts characters after the percent sign that are not
hexadecimal digits. Some of these translate to printable ASCII characters, and
this could provide an alternate means of specifying files in URLs.

It is possible when using the Internet Database Connector (IDC) to create links,
or you are using the return value arguments passed to other documents. When this
happens you may be unable to pass arguments that contain spaces.

IIS 4.0 may improperly translate non-hexadecimal characters preceded by a percent
sign. For example %3p is translated into an \\\"I\\\".

The vulnerability does not affect IIS; even specifying a file name through this
alternate method does not bypass IIS access controls. However, third-party
software that runs atop IIS but does not perform canonicalization, is affected
by it.

RESOLUTION
==========

Windows NT 4.0
--------------

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

  US English:

  x86: DownloadDownload Unschx4i.exe now
  (http://www.microsoft.com/Downloads/Release.asp?ReleaseID=16357)
  Alpha: DownloadDownload Unschx4a.exe now
  (http://www.microsoft.com/Downloads/Release.asp?ReleaseID=16358)

  Dutch:

  x86: DownloadDownload Unschx4i.exe now
  (http://www.microsoft.com/Downloads/Release.asp?ReleaseID=18985)
  Alpha: DownloadDownload Unschx4a.exe now
  (http://www.microsoft.com/Downloads/Release.asp?ReleaseID=18984)

  French:

  x86: DownloadDownload Unschx4i.exe now
  (http://www.microsoft.com/Downloads/Release.asp?ReleaseID=18983)
  Alpha: DownloadDownload Unschx4a.exe now
  (http://www.microsoft.com/Downloads/Release.asp?ReleaseID=18982)

  German:

  x86: DownloadDownload Unschx4i.exe now
  (http://www.microsoft.com/Downloads/Release.asp?ReleaseID=16359)
  Alpha: DownloadDownload Unschx4a.exe now
  (http://www.microsoft.com/Downloads/Release.asp?ReleaseID=16360)

  Japanese:

  x86: DownloadDownload Unschx4i.exe now
  (http://www.microsoft.com/Downloads/Release.asp?ReleaseID=16361)
  Alpha: DownloadDownload Unschx4a.exe now
  (http://www.microsoft.com/Downloads/Release.asp?ReleaseID=16362)

  Korean:

  x86: DownloadDownload Unschx4i.exe now
  (http://www.microsoft.com/Downloads/Release.asp?ReleaseID=16363)
  Alpha: DownloadDownload Unschx4a.exe now
  (http://www.microsoft.com/Downloads/Release.asp?ReleaseID=16364)

  Portuguese (Brazilian)

  x86: DownloadDownload Unschx4i.exe now
  (http://www.microsoft.com/Downloads/Release.asp?ReleaseID=18979)
  Alpha: DownloadDownload Unschx4a.exe now
  (http://www.microsoft.com/Downloads/Release.asp?ReleaseID=18978)

  Simplified Chinese:

  x86: DownloadDownload Unschx4i.exe now
  (http://www.microsoft.com/Downloads/Release.asp?ReleaseID=16351)
  Alpha: DownloadDownload Unschx4a.exe now
  (http://www.microsoft.com/Downloads/Release.asp?ReleaseID=16354)

  Spanish:

  x86: DownloadDownload Unschx4i.exe now
  (http://www.microsoft.com/Downloads/Release.asp?ReleaseID=18981)
  Alpha: DownloadDownload Unschx4a.exe now
  (http://www.microsoft.com/Downloads/Release.asp?ReleaseID=18980)

  Traditional Chinese:

  x86: DownloadDownload Unschx4i.exe now
  (http://www.microsoft.com/Downloads/Release.asp?ReleaseID=16355)
  Alpha: DownloadDownload Unschx4a.exe now
  (http://www.microsoft.com/Downloads/Release.asp?ReleaseID=16356)

  Swedish:

  x86: DownloadDownload Unschx4i.exe now
  (http://www.microsoft.com/Downloads/Release.asp?ReleaseID=18987)
  Alpha: DownloadDownload Unschx4a.exe now
  (http://www.microsoft.com/Downloads/Release.asp?ReleaseID=18986)

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.



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 this to be a problem in Internet Information Server 4.0.

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

For related information about this problem, please visit the following Microsoft
Web site:

  http://www.microsoft.com/security/bulletins/MS99-061.asp

For additional security-related information about Microsoft products, please
visit the following Microsoft Web site:

  http://www.microsoft.com/security/

Additional query words: iisscript asp iiswww iisvirtual security_patch tsesrp

======================================================================
Keywords          : kbSecurity kbOSWinNT400sp4 kbiis400 kbOSWinNT400sp6 kbWinNT400PreSP7Fix 
Technology        : kbWinNTsearch kbWinNT400search kbWinNTSsearch kbWinNTS400sp6 kbWinNTS400sp5 kbWinNTS400sp4 kbWinNTS400sp3 kbWinNTS400search kbSiteServSearch kbiisSearch kbAudDeveloper kbiis400 kbSiteServ300
Version           : :3.0,4.0,4.0 SP3,4.0 SP4,4.0 SP5,4.0 SP6
Hardware          : ALPHA x86
Issue type        : kbbug
Solution Type     : kbfix

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