Virtual Directory Mapped to UNC Returns Server-Side Script Code When URL Contains Additional Characters at the End of the Request (249599)


The information in this article applies to:

  • Microsoft Internet Information Server 4.0
  • Microsoft Internet Information Services 5.0
This article was previously published under Q249599

SYMPTOMS

If a virtual directory on an Internet Information Server (IIS) computer is mapped to a Universal Naming Convention (UNC) share, and a request for a file in the directory contains one of several particular characters at the end of the request, the expected Internet Server Application Programming Interface (ISAPI) extension processing may not occur. This can result in the source code of the file being sent to the browser.

CAUSE

This problem can be caused by the use of a varying combination of special characters at the end of the clients request.

RESOLUTION

Windows 2000

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:

260910 How to Obtain the Latest Windows 2000 Service Pack

This fix is also available individually. The following files are available for download from the Microsoft Download Center:

US English
DownloadDownload Q249599_W2K_SP1_X86_EN.EXE now

Arabic
DownloadDownload Q249599_W2K_SP1_X86_AR.EXE now

Chinese (Simplified)
DownloadDownload Q249599_W2K_SP1_X86_CN.EXE now

Chinese (Traditional)
DownloadDownload Q249599_W2K_SP1_X86_TW.EXE now

Dutch
DownloadDownload Q249599_W2K_SP1_X86_NL.EXE now

French
DownloadDownload Q249599_W2K_SP1_X86_FR.EXE now

German
DownloadDownload Q249599_W2K_SP1_X86_DE.EXE now

Hebrew
DownloadDownload Q249599_W2K_SP1_X86_HE.EXE now

Italian
DownloadDownload Q249599_W2K_SP1_X86_IT.EXE now

Japanese
DownloadDownload Q249599_W2K_SP1_X86_JA.EXE now

Korean
DownloadDownload Q249599_W2K_SP1_X86_KO.EXE now

Portuguese (Brazil)
DownloadDownload Q249599_W2K_SP1_X86_BR.EXE now

Spanish
DownloadDownload Q249599_W2K_SP1_X86_ES.EXE now

Swedish
DownloadDownload Q249599_W2K_SP1_X86_SV.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:

119591 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.




Windows NT 4.0

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

US English
x86: DownloadDownload Uncsec4i.exe now
Alpha: DownloadDownload Uncsec4a.exe now

Dutch
x86: Download Uncsec4i.exe now
Alpha: Download Uncsec4a.exe now

French
x86: Download Uncsec4i.exe now
Alpha: Download Uncsec4a.exe now

German
x86: Download Uncsec4i.exe now
Alpha: Download Uncsec4a.exe now

NOTE: Debug symbol files are required by an administrator to do both kernel and user mode debugging, providing a method to resolve global variables and function names in the loaded executable file. Click the file names below to download the symbol files:

German x86 Symbols: Download Uncsec4is.exe now
German Alpha Symbols: Download Uncsec4as.exe now

Portuguese (Brazilian)
x86: DownloadDownload Uncsec4i.exe now
Alpha: Download Uncsec4a.exe now

Spanish
x86: Download Uncsec4i.exe now
Alpha: DownloadDownload Uncsec4a.exe now

Swedish
x86: Download Uncsec4i.exe now
Alpha: Download Uncsec4a.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:

119591 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 security-enhanced servers that help to 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
   -------------------------------------------------------------
   12/28/99  06:02p  4.2.736.1  185,248   Infocomm.dll  x86
   12/28/99  06:03p  4.2.736.1   38,256   Ssinc.dll     x86
   12/28/99  06:03p  4.2.736.1   25,360   Sspifilt.dll  x86
   12/28/99  06:03p  4.2.736.1  228,464   W3svc.dll     x86

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:

317636 Windows NT Server 4.0, Terminal Server Edition, Security Rollup Package

STATUS

Windows 2000

Microsoft has confirmed that this is a problem in Internet Information Services 5.0. This problem was first corrected in Windows 2000 Service Pack 1.

Windows NT 4.0

Microsoft has confirmed that this is a problem in Internet Information Server 4.0.

MORE INFORMATION

There are significant restrictions that increase the difficulty of exploiting this vulnerability:
  • By design, virtual directories hide the actual location of files. Under most circumstances, there is no way for an attacker to determine which files on a server actually reside on a UNC share.
  • Many browsers "correct" requests that contain the trailing characters at issue here by either removing the characters or changing them.
  • If recommended security practices are followed, ASP and other files that require server-side processing will not contain any sensitive information to compromise.
This fix eliminates the vulnerability by removing the trailing special characters if they are included in the request. This causes the appropriate scripting engine to process the file when the request is returned to the browser. If the request is improperly formatted, the request is denied, and then returned to the client as an invalid request.

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

http://www.microsoft.com/technet/security/bulletin/ms00-019.mspx

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

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

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

249149 Installing Microsoft Windows 2000 and Windows 2000 Hotfixes

Modification Type:MinorLast Reviewed:6/1/2006
Keywords:kbdownload kbbug kbfix kbgraphxlinkcritical kbSecurity kbHotfixServer kbQFE KB249599
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