David Litchfield of Next Generation Security Software discovered that a buffer-overflow vulnerability exists in Microsoft Data Access Components (MDAC) that could result in the SQL Server service failing orexecuting arbitrary code from a potential attacker. This vulnerability results from an unchecked buffer in the MDAC functions  that handle the OpenRowSet command. Microsoft has released Security Bulletin MS02-040 (Unchecked Buffer in MDAC Function Could Enable SQL Server Compromise) to address this vulnerability and recommends that affected users apply the appropriate patch mentioned in the bulletin.

http://www.secadministrator.com/articles/index.cfm?articleid=26126 .