"Microsoft is aware that exploit code has been published on the Internet for the vulnerability addressed by this advisory," the company said in a bulletin published Monday.
The threat is essentially software code that hackers could use to access or alter corporate databases built with SQL Server. The malicious code could allow what's known in IT security as remote code execution, a process by which hackers could, for instance, alter figures in a bank account without ever setting foot on the bank's premises.
Microsoft said SQL Server 2000, SQL Server 2005, SQL Server 2005 Express Edition, SQL Server 2000 Desktop Engine, and Windows Internal Database (WYukon) are all potentially vulnerable to the threat. It added, however, that it's not aware of any attacks having actually been carried out.
The threat does not affect SQL Server 7.0 Service Pack 4, SQL Server 2005 Service Pack 3, or SQL Server 2008, Microsoft said.
"This vulnerability is not exposed anonymously. An attacker would need to either authenticate to exploit the vulnerability or take advantage of a SQL injection vulnerability in a Web application that is able to authenticate," Microsoft noted in its security bulletin.
Microsoft said it's continuing to investigate the problem and will issue a security patch if necessary -- either as a special download or as part of its regular monthly security update cycle.
In the meantime, Microsoft is urging customers who believe they've been targeted by hackers using the vulnerability to contact Microsoft customer service, as well as the Federal Bureau of Investigation and the Internet Crime Complaint Center.