A security vulnerability results because of an unchecked buffer in the IMC code that generates the response to the EHLO protocol command. If the buffer were overrun with data it would result in either the failure of the IMC or could allow the attacker to run code in the security context of the IMC, which runs as Exchange5.5 Service Account. ** OVS only uses the banner header to determine if this vulnerability exists and does not check for or attempt an actual overflow.

see http://www.microsoft.com/technet/security/bulletin/MS02-037.mspx