Bulletin Severity Rating:Critical - This security update resolves three privately reported vulnerabilities in Windows Print Spooler. The most severe vulnerability could allow remote code execution if an affected server received a specially crafted RPC request. Firewall best practices and standard default firewall configurations can help protect networks from attacks that originate outside the enterprise perimeter. Best practices recommend that systems that are connected to the Internet have a minimal number of ports exposed.

Read more at: Microsoft Security Bulletins