The flaw affects the Microsoft Data Access Components (MDAC), which provide database access for Windows platforms, according to a statement from Foundstone, a software vulnerability management company that discovered the flaw.
Microsoft said certain versions of Windows NT, Windows 2000 and Windows Me are vulnerable, with other versions of its operating system potentially at risk. Windows XP users are unaffected and need take no action.
The company deemed the vulnerability "critical" by Microsoft, the highest possible rating under the company's new rating system, which was announced on 19 November.
The company defines critical vulnerabilities as those "whose exploitation could allow the propagation of an Internet worm such as Code Red or Nimda without user action."
The hole is particularly menacing because of the large number of systems that are vulnerable and because of the ease with which existing worms such as Code Red or Nimda could be modified to take advantage of the newly disclosed flaw, said Stuart McClure, Foundstone's president and chief technical officer.
"What makes it really quite dangerous is that it can be easily added to a worm," McClure said.
"It's very much in line with Code Red and Nimda because of the attack vectors and the ways that it attacks. But with this vulnerability both the server and client component can be attacked, as opposed to Code Red and Nimda, which basically exploited server-based vulnerabilities and didn't take advantage of a browser-based vulnerability like this," he said.
Foundstone discovered the vulnerability in August and disclosed the information to Microsoft at that time, McClure said.
The vulnerability affects code that is installed and implemented by default in Windows 2000, and within the Windows NT 4.0 option pack.
Machines running Internet Explorer versions 5.01, 5.5 and 6.0 are also affected by the new vulnerability.
Microsoft's security bulletin MS02-065, is at www.microsoft.com/technet/treeview/default.asp?url=/technet/security/bulletin/MS02-065.asp
The patch is at www.microsoft.com/downloads/Release.asp?ReleaseID=44733