Today we released security bulletin MS11-034 to address vulnerabilities in the win32k subsystem. This update addresses externally reported issues as well as several internally found vulnerabilities that were discovered as part of our variant investigation.
The bulletin may appear to address an alarmingly large number of issues. However, if you dig into the issues themselves, you’ll find that the 30 vulnerabilities addressed in this update really just share three separate vulnerability root causes: insufficient validation or locking of win32k objects after a user-mode callback.