Software Engineering Institute

Microsoft Windows recognizes resources identified by the Uniform Naming Convention (UNC). Requests for resources identified by UNC references are routed through a service called the Multiple UNC Provider (MUP). MUP determines which subsystem provides the resource in question, and invokes the subsystem as needed. A buffer overflow in the MUP service could allow a local attacker to execute arbitrary code with the privileges of the operating system. Quoting from Microsoft Security Bulletin MS02-017,

When MUP receives a file request, it allocates a buffer in which to store it. There is proper input checking in this first buffer. However, MUP stores another copy of the file request in a buffer when it sends this request to a redirector. This second copy of the buffer does not check inputs correctly, thereby creating the possibility that a resource request to it from an unprivileged process could cause a buffer overrun. The overrun could be exploited for either of two purposes: causing a system failure, or running code on the system with Local System privileges.

This problem affects many versions of Windows, but it is more difficult to exploit this problem to execute code on Windows 2000 than other versions of Windows.

Local intruders can exploit arbitrary code with the privileges of the operating system. If an intruder gains access to a sensitive server such as a domain controller, he may be able to control the operations of that server and other machines which rely on that server.

Apply a patch as described in http://www.microsoft.com/technet/treeview/default.asp?url=/technet/security/bulletin/MS02-017.asp.