An elevation of privilege vulnerability exists when Microsoft Windows improperly handles reparse points. An attacker who successfully exploited this vulnerability could overwrite or delete a targeted file that would normally require elevated permissions. To exploit this vulnerability, an attacker would first have to log on to the system. An attacker could then run a specially crafted application that could exploit the vulnerability and overwrite or delete files. The security update addresses the vulnerability by correcting how Windows handles reparse points.
Donato Ferrante of IOActive