DOCUMENT:Q295534 15-AUG-2002 [iis] TITLE :Superfluous Decoding Operation Can Allow Command Execution 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 Services version 5.0 - Microsoft Internet Information Server version 4.0 ------------------------------------------------------------------------------- SYMPTOMS ======== A vulnerability exists in Microsoft Internet Information Services (IIS) 5.0 and Microsoft Internet Information Server (IIS) 4.0 that can enable a malicious user to run (execute) operating system commands on an affected Web server. This gives the malicious user the ability to modify Web pages, add, change, or delete files, reformat the hard disk, or take other actions (such as uploading any code to the server and running it). Best practices, if followed, can make it difficult or impossible for an attacker to exploit the vulnerability. Even if an attacker successfully exploits it, the vulnerability does not grant the attacker administrative control over the server. Instead, the vulnerability grants the attacker privileges that are normally reserved for a user who can log on to the server interactively. Nevertheless, even these privileges can enable a malicious user to cause widespread damage and allow a point from which the malicious user can launch additional attacks in the hope of gaining additional privileges. Mitigating Factors: - This vulnerability does not provide a way for the attacker to learn the folder structure on the server. As a result, if the operating system is installed on a separate drive from the Web root or in non-standard folders, it can prevent an attacker from locating programs of interest. - This vulnerability does not provide administrative access to the server. If you followed the recommendations in the IIS 4.0 and IIS 5.0 security checklists, sensitive programs are moved to folders that only the administrator can access, and non-administrative access to server resources is severely restricted. CAUSE ===== This vulnerability occurs because of an error in the functionality that processes requests to run programs that are housed on the server. A superfluous decoding operation could give an attacker the opportunity to bypass security checks and escape the server's virtual folder structure, thereby enabling the attacker to run operating system commands on the server. RESOLUTION ========== For additional information on what is fixed by the following patches, click the article number below to view the article in the Microsoft Knowledge Base: Q297860 IIS 5.0 Security and Post-Windows NT 4.0 SP5 IIS 4.0 Patch Rollup 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 file is available for download from the Microsoft Download Center: DownloadDownload Q293826_W2K_SP3_x86_en.exe now (http://www.microsoft.com/Downloads/Release.asp?ReleaseID=29764) 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 -------------------------------------------------------- 05/04/2001 11:48a 5.0.2195.3407 245,520 Adsiis.dll 05/04/2001 11:48a 5.0.2195.3407 332,560 Asp.dll 08/26/2000 06:30p 6,512 Fixerr.js 11/10/2000 11:21p 5.0.2195.3407 593,976 Fp4autl.dll 03/27/2001 10:10p 5.0.2195.3407 445,712 Httpext.dll 05/04/2001 11:48a 5.0.2195.3407 56,592 Httpodbc.dll 05/04/2001 11:48a 5.0.2195.3407 122,640 Iisrtl.dll 05/04/2001 11:48a 5.0.2195.3407 13,584 Infoadmn.dll 05/04/2001 11:48a 5.0.2195.3407 245,520 Infocomm.dll 05/04/2001 11:48a 5.0.2195.3407 62,736 Isatq.dll 05/04/2001 11:48a 5.0.2195.3407 46,352 Ism.dll 05/04/2001 11:48a 5.0.2195.3407 76,560 Msw3prt.dll 10/17/2000 01:38p 5.0.2195.3407 6,928 Schmupd.exe 05/04/2001 11:48a 5.0.2195.3407 41,232 Ssinc.dll 05/04/2001 11:48a 5.0.2195.3407 7,440 W3ctrs.dll 05/04/2001 11:48a 5.0.2195.3407 357,648 W3svc.dll NOTE: You can install this patch on systems that are running Microsoft Windows 2000 Gold, Windows 2000 Service Pack 1, or Windows 2000 Service Pack 2. Internet Information Server 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) A supported fix is now available from Microsoft, but it is only intended to correct the problem that is described in this article. Apply it only to computers that you determine are at risk of attack. Evaluate your computer's physical accessibility, network and Internet connectivity, and other factors to determine the degree of risk to your computer. See the associated Microsoft Security Bulletin (http://www.microsoft.com/technet/security/bulletin/ms01-026.asp) to help determine the degree of risk. This fix may receive additional testing. If your computer is sufficiently at risk, Microsoft recommends that you apply this fix now. To resolve this problem immediately, download the fix by clicking the download link later in this article or contact Microsoft Product Support Services to obtain the fix. For a complete list of Microsoft Product Support Services phone numbers and information about support costs, please visit the following Microsoft Web site: http://support.microsoft.com/default.aspx?scid=fh;EN-US;CNTACTMS NOTE: In special cases, charges that are ordinarily incurred for support calls may be canceled, if a Microsoft Support Professional determines that a specific update will resolve your problem. The usual support costs will apply to additional support questions and issues that do not qualify for the specific update in question. The following file is available for download from the Microsoft Download Center: DownloadDownload Q295534i.exe now (http://www.microsoft.com/Downloads/Release.asp?ReleaseID=29787) NOTE: Q295534is.exe are the Symbols files. 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 ------------------------------------------------------------------ 04/11/2001 01:32p 4.2.764.1 214,544 Adsiis.dll x86 04/11/2001 01:33p 4.2.764.1 330,672 Asp.dll x86 04/02/2001 04:55p 4.0.2.4701 593,976 Fp4autl.dll x86 04/11/2001 01:32p 4.2.764.1 81,888 Ftpsvc2.dll x86 04/11/2001 01:32p 4.2.764.1 55,392 Httpodbc.dll x86 04/11/2001 01:32p 4.2.764.1 98,912 Iischema.dll x86 04/11/2001 01:31p 4.2.764.1 63,472 Iislog.dll x86 04/11/2001 01:31p 4.2.764.1 185,792 Infocomm.dll x86 04/11/2001 01:31p 4.2.764.1 29,520 Iscomlog.dll x86 04/11/2001 01:35p 4.2.764.1 54,560 Ism.dll x86 04/02/2001 04:55p 4.0.1381.7086 375,056 Kernel32.dll x86 04/11/2001 01:36p 4.2.764.1 9,680 Schmupd.exe x86 04/11/2001 01:32p 4.2.764.1 38,256 Ssinc.dll x86 04/11/2001 01:32p 4.2.764.1 25,360 Sspifilt.dll x86 04/11/2001 01:32p 4.2.764.1 229,024 W3svc.dll x86 04/11/2001 01:31p 4.2.764.1 88,032 Wam.dll x86 08/20/1999 12:26a 4.0.1381.321 171,280 W3svc.dll Alpha NOTE: You can install this patch on systems that are running Microsoft Windows NT 4.0 Service Pack 5 or Windows NT 4.0 Service Pack 6a. 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 ====== Internet Information Services 5.0 --------------------------------- Microsoft has confirmed that this problem may cause a degree of security vulnerability in Internet Information Services 5.0. This problem was first corrected in Windows 2000 Service Pack 3. Internet Information Server 4.0 ------------------------------- Microsoft has confirmed that this problem may cause a degree of security vulnerability in Internet Information Server 4.0. 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 vulnerability, see the following Microsoft Web site: http://www.microsoft.com/technet/security/bulletin/ms01-026.asp Additional query words: kbIISCom security_patch kbWin2000srp1 ====================================================================== Keywords : kbSecurity kbCOMIS kbWinNT400PreSP7Fix kbWin2000PreSP3Fix kbgraphxlinkcritical KbSECVulnerability 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.