MS02-018: Patch available for buffer overrun in HTTP header handling vulnerability

A buffer overrun (http://www.microsoft.com/security/portal/glossary.aspx) vulnerability exists in Internet Information Server (IIS) 4.0, Internet Information Services (IIS) 5.0, and IIS 5.1. By sending a specially chosen request to an affected Web server, an attacker can either disrupt Web services or gain the ability to run a program on the server. Such a program runs with full system permissions in IIS 4.0, and with fewer, but still significant, permissions in IIS 5.0 and 5.1.

Customers who have used the IIS Lockdown Tool (http://www.microsoft.com/technet/security/tools/locktool.mspx) to configure their servers as static Web servers are already protected against this vulnerability. The URLScan (http://technet.microsoft.com/en-us/security/cc242650.aspx) tool, if it is deployed with the default rule set, also makes it hard to use the vulnerability to gain control of the server, and likely reduces the vulnerability to only a denial-of-service attack.

This vulnerability results because of an error that occurs when Active Server Pages (ASP) parses HTTP header information. An initial check is performed to make sure that certain expected characters are present and can be used to end a copy operation. However, the check can be spoofed, thereby enabling a copy operation that does not end to overrun a buffer.

Internet Information Services 5.1

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

Internet Information Services 5.0

The update for this problem is included in the "MS02-018: April 2002 Cumulative Patch for Internet Information Services." For more information about how to obtain this patch, click the following article number to view the article in the Microsoft Knowledge Base: To resolve this problem, obtain the latest service pack for Windows 2000. For more information, click the following article number to view the article in the Microsoft Knowledge Base:

Internet Information Server 4.0

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

Internet Information Services 5.1

Microsoft has confirmed that this problem may cause a degree of security vulnerability in Microsoft Internet Information Services 5.1.

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.

For more information on these vulnerabilities, see the following Microsoft Web site: For more information about how to obtain a hotfix for Windows 2000 Datacenter Server, click the following article number to view the article in the Microsoft Knowledge Base: For more information on how to install multiple hotfixes with only one reboot, click the following article number to view the article in the Microsoft Knowledge Base: