Microsoft KB Archive/318091

= MS02-018: Patch Available for Buffer Overrun in HTR ISAPI Extension Vulnerability =

Article ID: 318091

Article Last Modified on 11/21/2006

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APPLIES TO


 * Microsoft Internet Information Services 5.0
 * Microsoft Internet Information Server 4.0

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This article was previously published under Q318091



SYMPTOMS
A buffer overrun vulnerability exists in Internet Information Server (IIS) 4.0 and Internet Information Services (IIS) 5.0. By sending a specially chosen request to an affected Web server, an attacker can cause the server to temporarily stop providing Web services or, in very unusual cases, the attacker can gain control of the server.

A number of factors, including the following, tend to reduce the severity of this vulnerability:
 * It is extremely hard to inject code by exploiting this vulnerability because the overrun is not on the stack and is only a single byte over the allocated buffer.
 * By default, the IIS Lockdown Tool removes the component that contains the vulnerability.
 * The default configuration of the URLScan tool prevents the vulnerability from being exploited.



CAUSE
This vulnerability occurs because the Internet Server Application Programming Interface (ISAPI) extension that implements HTR scripting contains an off-by-one error when it calculates the size of a buffer for storing an input value. If a request for an HTR script is malformed in a particular way, it is possible to abuse the miscalculation and conduct a buffer overrun attack. In the least serious case, this can result in the failure of the IIS service; in the most serious case (which is very hard to exploit), it can allow code to be run on the server.



Internet Information Services 5.0
The update for this problem is included in the &quot;MS02-018: April 2002 Cumulative Patch for Internet Information Services&quot;. For additional information about how to obtain this patch, click the article number below to view the article in the Microsoft Knowledge Base:

319733 MS02-018: April 2002 Cumulative Patch for Internet Information Services

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

Internet Information Server 4.0
The update for this problem is included in the &quot;MS02-018: April 2002 Cumulative Patch for Internet Information Services&quot;. For additional information about how to obtain this patch, click the article number below to view the article in the Microsoft Knowledge Base:

319733 MS02-018: April 2002 Cumulative Patch for Internet Information Services



Internet Information Services 5.0
Microsoft has confirmed that this problem may cause a degree of security vulnerability in Microsoft 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 Microsoft Internet Information Server 4.0.



MORE INFORMATION
For more information on these vulnerabilities, see the following Microsoft Web site:

http://www.microsoft.com/technet/security/bulletin/MS02-018.mspx

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 Datacenter Program and Windows 2000 Datacenter Server Product

For additional information on 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

Additional query words: kbIISCom kbIIS400500510April2002Rollup security_patch

Keywords: kbbug kbfix kbwin2000presp3fix kbqfe kbwin2000sp3fix kbsecurity kbhotfixserver KB318091

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