A denial of service vulnerability exists in Windows Domain Name System (DNS) DNSAPI.dll when it fails to properly handle DNS responses. An attacker who successfully exploited the vulnerability could cause a system to stop responding. Note that the denial of service condition would not allow an attacker to execute code or to elevate user privileges. However, the denial of service condition could prevent authorized users from using system resources. To exploit the vulnerability, the attacker would use a malicious DNS server to send corrupted DNS responses to the target. The update addresses the vulnerability by modifying how Windows DNSAPI.dll handles DNS responses.