An elevation of privilege vulnerability exists in the way that the Wininit.dll handles objects in memory. An attacker who successfully exploited the vulnerability could execute code with elevated permissions.
There are multiple ways an attacker could exploit the vulnerability:
In a web-based attack scenario, an attacker could host a specially crafted website that is designed to exploit this vulnerability and then convince a user to view the website. An attacker would have no way to force users to view the attacker-controlled content. Instead, an attacker would have to convince users to take action, typically by getting them to click a link in an email message or in an Instant Messenger message that takes users to the attacker's website, or by opening an attachment sent through email.
In a file sharing attack scenario, an attacker could provide a specially crafted document file that is designed to exploit this vulnerability, and then convince a user to open the document file.
The security update addresses the vulnerability by ensuring the Wininit.dll properly handles objects in memory.