Microsoft KB Archive/234905

= Improperly Formatted HTTP Request May Cause INETINFO Process to Fail =

Article ID: 234905

Article Last Modified on 9/4/2007

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APPLIES TO


 * Microsoft Windows NT Server 4.0, Terminal Server Edition
 * Microsoft Internet Information Server 4.0

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This article was previously published under Q234905



SYMPTOMS
When a Web site visitor requests a selected file mapping, the request is mapped to an appropriate DLL for processing the visitor's request. The appropriate DLL may include any Microsoft DLL or an installed third-party filter DLL. A problem currently exists in the Microsoft DLLs for handling an improperly formatted request that uses an HTR, STM, or IDC application mapping. There is the possibility that this problem could be exploited by a malicious Web user by sending an improperly formatted HTTP request to a Microsoft Internet Information Server (IIS) computer, which can result in the unstable operation of the Web server.



WORKAROUND
Microsoft has provided a patch to correct this problem; however, additional steps can be used to prevent issues similar to this one from impacting any Microsoft IIS 4.0 computer. Selecting Check if file Exists in the script application mappings section of the ISM forces IIS 4.0 to check if the requested script exists or if the user has permission to the requested script. If not, the appropriate warning message is returned to the browser and the script engine is not invoked.

To select Check if file Exists, perform the following steps:
 * 1) In the Internet Service Manager (ISM), double-click Internet Information Server.
 * 2) Right-click the computer name and then click Properties.
 * 3) In the Master Properties drop-down box, click WWW Service, and then click Edit.
 * 4) Click the Home Directory tab, and then click Configuration.
 * 5) Double-click the line in the extension mappings that contains .HTR.
 * 6) Select the Check if file exists check box.
 * 7) Repeat these steps for the STM and IDC application mappings.
 * 8) Close the ISM.

NOTE: When you choose to use this option, the originating TCP\IP address of the request and the response is logged in the IIS log if IIS logging is turned on.



Windows NT Server or Workstation 4.0
To resolve this problem, obtain the latest service pack for Windows NT 4.0 or the individual software update. For information on obtaining the latest service pack, please go to:


 * http://www.microsoft.com/windows/servicepacks/ -or-


 * 152734how to obtain the latest windows nt 4.0 service pack

For information on obtaining the individual software update, contact Microsoft Product Support Services. For a complete list of Microsoft Product Support Services phone numbers and information on support costs, please go to the following address on the World Wide Web:

http://support.microsoft.com/directory/overview.asp

Windows NT Server 4.0, Terminal Server Edition
To resolve this problem, obtain the latest service pack for Windows NT Server 4.0, Terminal Server Edition. For additional information, click the following article number to view the article in the Microsoft Knowledge Base:

152734 How to Obtain the Latest Windows NT 4.0 Service Pack



STATUS
Microsoft has confirmed that this is a problem in Windows NT 4.0 and Windows NT Server 4.0, Terminal Server Edition.

This problem was first corrected in Windows NT Server 4.0 Service Pack 6 and Windows NT Server 4.0, Terminal Server Edition Service Pack 6.



MORE INFORMATION
The effected application mappings are IDC, HTR, and STM.

HTR files enable remote administration of user passwords.IDC Internet Database Connector files allows an Internet application to query and update backend database.STM is used for server-side Include files.

Please see the following Microsoft Security Bulletin (MS99-019) for more information related to this issue:

Patch Available for "Malformed HTR Request" Vulnerability

For additional security-related information about Microsoft products, please visit:

http://www.microsoft.com/security

Keywords: kbhotfixserver kbqfe kbbug kbfix kbqfe KB234905

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