Microsoft has released a new security patch for Windows NT 4.0, Windows 2000, and Windows 98

The Windows Shell is responsible for providing the basic framework of the Windows user interface experience. It is most familiar to users as the Windows Desktop, but also provides a variety of other functions to help define the user's computing session, including organizing files and folders, and providing the means to start applications.

An unchecked buffer exists in one of the functions that helps to locate incompletely removed applications on the system. A security vulnerability results because it is possible for a malicious user to mount a buffer overrun attack and attempt to exploit this flaw. A successful attack would have the affect of either causing the Windows Shell to crash, or causing code to run in the user's context.

Be default, this is not remotely exploitable. However, under very unusual conditions, it could be exploited via a web page - - specifically, if the user has installed an application with custom URL handlers and then uninstalled that application, and the uninstall failed to correctly remove the application completely. An attacker could then attempt to levy an attack by constructing an HTML web page that seeks to exploit the vulnerability, and then posting it on their web site or sending it by email.

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