The vulnerability exists in editions of Windows XP, Server 2003 and Vista, as well as IE versions 5, 6 and 7, when the operating system or browser resolves hostnames that do not include a fully qualified domain name.
Tim Rains, Microsoft security response communications lead, said today that his company has received no reports of public exploitation of the flaw.
Microsoft users who do not have a primary DNS (Domain Name system) suffix configured on their system, whose DNS domain name is registered as a second-level domain or who have specified a proxy server via DHCP (Dynamic Host Configuration Protocol) server settings are not affected by the flaw.
The vulnerability also does not affect customers who have a trusted WPAD server, who have manually specified a proxy server in IE, or who have disabled the “Automatically Detect Settings” option in IE.
Microsoft credited Beau Butler with reporting the flaw.