Description: This security update resolves one publicly disclosed and two privately reported vulnerabilities in Server Message Block Version 2 (SMBv2). The most severe of the vulnerabilities could allow remote code execution if an attacker sent a specially crafted SMB packet to a computer running the Server service. Firewall best practices and standard default firewall configurations can help protect networks from attacks that originate from outside the enterprise perimeter. Best practices recommend that systems that are connected to the Internet have a minimal number of ports exposed. The security update addresses the vulnerabilities by correctly validating the fields inside the SMBv2 packets, correcting the way that SMB handles the command value in SMB packets, and correcting the way that SMB parses specially crafted SMB packets.

Update type: Critical

Release date: October 13, 2009

Applies to: All versions

Knowledge base: support.microsoft.com/kb/975517

Download link: 32-bit | 64-bit
Comments:Here are the specifics on the vulnerabilities covered by this update:

• SMBv2 Infinite Loop Vulnerability – CVE-2009-2526
• SMBv2 Command Value Vulnerability – CVE-2009-2532
• SMBv2 Negotiation Vulnerability – CVE-2009-3103