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Pattern-Matching Function Can Cause Access Violation on FTP Server


The information in this article applies to:
  • Microsoft Internet Information Services version 5.0
  • Microsoft Internet Information Server 4.0


SYMPTOMS

A denial of service (DoS) vulnerability exists in Microsoft Internet Information Services (IIS) 5.0 and Microsoft Internet Information Server (IIS) 4.0 because the function that processes wildcard sequences in FTP commands does not always allocate sufficient memory when it performs pattern matching. Under unusual circumstances, it may be possible for an attacker to levy an FTP command containing a wildcard sequence that, when expanded, can overrun the allocated memory and cause an access violation.

This scenario can cause the IIS service (which provides both Web and FTP functionality) to fail. As a result, all Web or FTP sessions that are in progress at the time are severed, and no new sessions can be established until the IIS service is restarted. In IIS 5.0, the service restarts automatically. In IIS 4.0, operator intervention is required to restart the service.

The attacker cannot add, change, or delete data on the server through this vulnerability, nor can the attacker usurp any administrative privileges.

Mitigating Factor

The attacker must be able to start an FTP session in order to exploit the vulnerability.


CAUSE

This problem occurs because of a flaw in a pattern-matching function that is used by at least one FTP command. Depending on the wildcard sequence that is entered and the specific configuration of the server's file system, it is possible for the resulting pattern to exceed the available memory and trigger an access violation. This, in turn, causes the IIS service to fail.


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

A supported fix is now available from Microsoft, but it is only intended to correct the problem described in this article and should be applied only to systems that are determined to be at risk of attack. Please evaluate your computer's physical accessibility, network and Internet connectivity, and other factors to determine the degree of risk to your computer. Please see the associated Microsoft Security Bulletin to help make this determination. This fix may receive additional testing at a later time, to further ensure product quality. If your computer is sufficiently at risk, Microsoft recommends that you apply this fix now. Otherwise, wait for the next Windows 2000 service pack that contains this fix.

To resolve this problem immediately, download the fix as instructed below or contact Microsoft Product Support Services to obtain the fix. 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
NOTE: In special cases, charges that are normally incurred for support calls may be canceled, if a Microsoft Support Professional determines that a specific update will resolve your problem. Normal 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:
[GRAPHIC: Download]Download Q293826_W2K_SP3_x86_en.exe now
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. Once posted, the file is housed 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  5.0.2195.3554  245,520  Adsiis.dll
   05/04/2001  11:48a  5.0.2195.3554  332,560  Asp.dll
   08/26/2000  06:30p                   6,512  Fixerr.js
   11/10/2000  11:21p  4.0.2.4701     593,976  Fp4autl.dll
   03/27/2001  10:10p  0.9.3940.21    445,712  Httpext.dll
   05/04/2001  11:48a  5.0.2195.3554   56,592  Httpodbc.dll
   05/04/2001  11:48a  5.0.2195.3554  122,640  Iisrtl.dll
   05/04/2001  11:48a  5.0.2195.3554   13,584  Infoadmn.dll
   05/04/2001  11:48a  5.0.2195.3554  245,520  Infocomm.dll
   05/04/2001  11:48a  5.0.2195.3554   62,736  Isatq.dll
   05/04/2001  11:48a  5.0.2195.3554   46,352  Ism.dll
   05/04/2001  11:48a  5.0.2195.3555   76,560  Msw3prt.dll
   10/17/2000  01:38p  5.0.2195.2507    6,928  Schmupd.exe
   05/04/2001  11:48a  5.0.2195.3554   41,232  Ssinc.dll
   05/04/2001  11:48a  5.0.2195.3554    7,440  W3ctrs.dll
   05/04/2001  11:48a  5.0.2195.3554  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

A supported fix is now available from Microsoft, but it is only intended to correct the problem described in this article and should be applied only to systems that are determined to be at risk of attack. Please evaluate your computer's physical accessibility, network and Internet connectivity, and other factors to determine the degree of risk to your computer. Please see the associated Microsoft Security Bulletin to help make this determination. This fix may receive additional testing at a later time, to further ensure product quality. If your computer is sufficiently at risk, Microsoft recommends that you apply this fix now.

To resolve this problem immediately, download the fix as instructed below or contact Microsoft Product Support Services to obtain the fix. 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
NOTE: In special cases, charges that are normally incurred for support calls may be canceled, if a Microsoft Support Professional determines that a specific update will resolve your problem. Normal 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:
[GRAPHIC: Download]Download Q295534i.exe now
NOTE: Q295534is.exe are the Symbols files.
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. Once posted, the file is housed 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
   --------------------------------------------------------
   04/11/2001  01:32p  4.2.764.1      214,544  Adsiis.dll
   04/11/2001  01:33p  4.2.764.1      330,672  Asp.dll
   04/02/2001  04:55p  4.0.2.4701     593,976  Fp4autl.dll
   04/11/2001  01:32p  4.2.764.1       81,888  Ftpsvc2.dll
   04/11/2001  01:32p  4.2.764.1       55,392  Httpodbc.dll
   04/11/2001  01:32p  4.2.764.1       98,912  Iischema.dll
   04/11/2001  01:31p  4.2.764.1       63,472  Iislog.dll
   04/11/2001  01:31p  4.2.764.1      185,792  Infocomm.dll
   04/11/2001  01:31p  4.2.764.1       29,520  Iscomlog.dll
   04/11/2001  01:35p  4.2.764.1       54,560  Ism.dll
   04/02/2001  04:55p  4.0.1381.7086  375,056  Kernel32.dll
   04/11/2001  01:36p  4.2.764.1        9,680  Schmupd.exe
   04/11/2001  01:32p  4.2.764.1       38,256  Ssinc.dll
   04/11/2001  01:32p  4.2.764.1       25,360  Sspifilt.dll
   04/11/2001  01:32p  4.2.764.1      229,024  W3svc.dll
   04/11/2001  01:31p  4.2.764.1       88,032  Wam.dll 
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.


STATUS

Microsoft has confirmed this to be a problem in the Microsoft products that are listed at the beginning of this article.


MORE INFORMATION

For more information on this vulnerability, see the following Microsoft Web site:

http://www.microsoft.com/technet/security/ms01-026
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:
Q249149 Installing Microsoft Windows 2000 and Windows 2000 Hotfixes

Additional query words: security_patch

Keywords : kbWinNT400PreSP7Fix kbWin2000PreSP3Fix
Issue type : kbbug
Technology : kbiisSearch kbExchange400 kbGraph500


Last Reviewed: May 15, 2001
© 2001 Microsoft Corporation. All rights reserved. Terms of Use.


Article ID: Q293826

Last Reviewed:
May 15, 2001

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