MS01-026: Pattern-Matching Function Can Cause Access Violation on FTP Server (293826)


The information in this article applies to:

  • Microsoft Internet Information Services 5.0
  • Microsoft Internet Information Server 4.0
This article was previously published under Q293826

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:

297860 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, 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

The English version of this fix should have the following file attributes or later:
   Date        Time    Version        Size     File name
   --------------------------------------------------------
   5/31/2001  03:31p  5.0.2195.3649  245,520    Adsiis.dll
   5/31/2001  03:31p  5.0.2195.3649  332,560    Asp.dll
   5/29/2001  04:37p  4.0.2.4701     593,976    Fp4autl.dll
   5/31/2001  03:31p  5.0.2195.3649  246,032    Httpext.dll
   5/31/2001  03:31p  5.0.2195.3649   56,592    Httpodbc.dll
   5/31/2001  03:31p  5.0.2195.3649  122,640    Iisrtl.dll
   5/31/2001  03:31p  5.0.2195.3649   13,584    Infoadmn.dll
   5/31/2001  03:31p  5.0.2195.3649  245,520    Infocomm.dll
   5/31/2001  03:31p  5.0.2195.3649   62,736    Isatq.dll
   5/31/2001  03:31p  5.0.2195.3649   46,352    Ism.dll
   5/31/2001  03:31p  5.0.2195.3649   76,560    Msw3prt.dll
   5/30/2001  03:40p  5.0.2195.3651     6928    Schmupd.exe
   5/30/2001  03:40p  5.0.2195.3651     7952    Spiisupd.exe
   5/31/2001  03:32p  5.0.2195.3649   41,232    Ssinc.dll
   5/31/2001  03:32p  5.0.2195.3649     7440    W3ctrs.dll
   5/31/2001  03:32p  5.0.2195.3649  353,040    W3svc.dll

Internet Information Server 4.0

A supported hotfix is now available from Microsoft, but it is only intended to correct the problem that this article describes. Apply it only to systems that you determine are at risk of attack. Evaluate the computer's physical accessibility, network and Internet connectivity, and other factors to determine the degree of risk to the computer. See the associated Microsoft Security Bulletin to help determine the degree of risk. This hotfix may receive additional testing. If the computer is sufficiently at risk, we recommend that you apply this hotfix now.

To resolve this problem immediately, download the hotfix by following the instructions later in this article or contact Microsoft Product Support Services to obtain the hotfix. For a complete list of Microsoft Product Support Services telephone numbers and information about support costs, visit the following Microsoft Web site:

http://support.microsoft.com/contactus/?ws=support

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
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:

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
   --------------------------------------------------------
   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

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:

265173 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:

296861 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.mspx

Modification Type:MinorLast Reviewed:10/13/2006
Keywords:kbHotfixServer kbQFE kbbug kbfix kbgraphxlinkcritical KbSECDOS KbSECHack kbSecurity KbSECVulnerability kbWin2000PreSP3Fix kbWin2000sp3fix KB293826
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