Microsoft rates MS09-001 as critical

Although there is only one Security Bulletin on this first Patch Tuesday of the New Year, it should not be dismissed. The patch issued today, MS09-001, resolves several privately reported vulnerabilities in Microsoft Server Message Block (SMB) Protocol, a protocol used for sharing files, printers, serial ports, and other communications.

Microsoft rates MS09-001 as critical, its highest rating, for users running Windows 2000, XP, and Server 2003, and moderate, its second highest rating, for users running Windows Vista and Server 2008. Installation of the patch will require a system restart.

There are three specific vulnerabilities addressed in today's bulletin. Microsoft says these flaws are unlikely to produce exploitable code because the first two (CVE-2008-4834 and CVE-2008-4835) only allow for one fixed value (zero) to be written and controlling what data is overwritten will also be difficult. The third vulnerability (CVE-2008-4114) affects all Windows systems and allows for a Denial of Service attack. It is because of the DoS threat that Microsoft recommends high priority updating of all SMB servers and Domain Controllers. Non-critical systems and those systems where SMB is blocked via a firewall could be considered less of a priority.

MS09-001 replaces the SMB patch MS08-063 issued last October