Microsoft SQL Server 2008 SP3, 2008 R2 SP2, and 2012 SP1 does not properly control use of stack memory for processing of T-SQL batch commands, which allows remote authenticated users to cause a denial of service (daemon hang) via a crafted T-SQL statement, aka "Microsoft SQL Server Stack Overrun Vulnerability."
https://docs.microsoft.com/en-us/security-updates/securitybulletins/2014/ms14-044
http://www.securitytracker.com/id/1030716