DOCUMENT:Q285985 15-AUG-2002 [iis] TITLE :New Variant of File Fragment Reading via .HTR Vulnerability PRODUCT :Internet Information Server PROD/VER::4.0,5.0 OPER/SYS: KEYWORDS:kbSecurity kbCOMIS kbWinNT400PreSP7Fix kbWin2000PreSP3Fix kbgraphxlinkcritical KbSECVul ====================================================================== ------------------------------------------------------------------------------- The information in this article applies to: - Microsoft Internet Information Server version 4.0 - Microsoft Internet Information Services version 5.0 ------------------------------------------------------------------------------- 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 ============================================================================= THE INFORMATION PROVIDED IN THE MICROSOFT KNOWLEDGE BASE IS PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND. MICROSOFT DISCLAIMS ALL WARRANTIES, EITHER EXPRESS OR IMPLIED, INCLUDING THE WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. IN NO EVENT SHALL MICROSOFT CORPORATION OR ITS SUPPLIERS BE LIABLE FOR ANY DAMAGES WHATSOEVER INCLUDING DIRECT, INDIRECT, INCIDENTAL, CONSEQUENTIAL, LOSS OF BUSINESS PROFITS OR SPECIAL DAMAGES, EVEN IF MICROSOFT CORPORATION OR ITS SUPPLIERS HAVE BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES. SOME STATES DO NOT ALLOW THE EXCLUSION OR LIMITATION OF LIABILITY FOR CONSEQUENTIAL OR INCIDENTAL DAMAGES SO THE FOREGOING LIMITATION MAY NOT APPLY. Copyright Microsoft Corporation 2002.