Microsoft SQL Server 2008 SP3 and SP4, 2008 R2 SP2 and SP3, 2012 SP1 and SP2, and 2014 does not prevent use of uninitialized memory in certain attempts to execute virtual functions, which allows remote authenticated users to execute arbitrary code via a crafted query, aka "SQL Server Remote Code Execution Vulnerability."
https://docs.microsoft.com/en-us/security-updates/securitybulletins/2015/ms15-058