Microsoft Security Bulletin MS03-007
Unchecked Buffer In Windows Component Could Cause Server Compromise (815021)
http://www.microsoft.com/technet/security/Bulletin/MS03-007.mspx
Microsoft originally released this security bulletin on March 17, 2003. At that time, Microsoft was aware of a publicly available exploit that was being used to attack Windows 2000 Servers running IIS 5.0. The attack vector in this case was WebDAV although the underlying vulnerability was in a core operating system component, ntdll.dll. Microsoft issued a patch to protect Windows 2000 customers shortly afterwards, but also continued to investigate the underlying vulnerability. During the course of that investigation, Microsoft found that Windows NT 4.0 also contains the underlying vulnerability in ntdll.dll, however it does not support WebDAV and therefore the known exploit was not effective against Windows NT 4.0. In addition, Microsoft has recently been made aware of this vulnerability as well in Windows XP. However, like Windows NT 4.0, Windows XP does not install Internet Information Services (IIS) by default. Microsoft has now released patches for Windows NT 4.0 and Windows XP.
Microsoft Windows 2000 supports the World Wide Web Distributed Authoring and Versioning (WebDAV) protocol. WebDAV, defined in RFC 2518, is a set of extensions to the Hyper Text Transfer Protocol (HTTP) that provide a standard for editing and file management between computers on the Internet. A security vulnerability is present in a Windows component used by WebDAV and results because a core operating system component, ntdll.dll, contains an unchecked buffer.
An attacker could exploit the vulnerability by sending a specially formed HTTP request to a machine running Internet Information Server (IIS). The request could cause the server to fail or to execute code of the attacker's choice. The code would run in the security context of the IIS service (which, by default, runs in the LocalSystem context).