A security feature bypass vulnerability exists in Microsoft Windows when a man-in-the-middle attacker is able to successfully bypass the NTLMv2 protection if a client is also sending LMv2 responses. An attacker who successfully exploited this vulnerability could gain the ability to downgrade NTLM security features.To exploit this vulnerability, the attacker would need to be able to modify NTLM traffic exchange.The update addresses the vulnerability by hardening NTLMv2 protection on the server-side.