Bulletin Severity Rating:Important - This security update resolves two publicly disclosed and two privately reported vulnerabilities in the Windows kernel that could allow elevation of privilege. An attacker who successfully exploited any of these vulnerabilities could execute arbitrary code and take complete control of an affected system. An attacker could then install programs; view, change, or delete data; or create new accounts with full user rights. An attacker must have valid logon credentials and be able to log on locally to exploit these vulnerabilities. The vulnerabilities could not be exploited remotely or by anonymous users.

Read more at: Microsoft Security Bulletins