The DNS Resolver Cache Service (aka DNSCache) in Windows DNS Server in Microsoft Windows 2000 SP4, Server 2003 SP1 and SP2, and Server 2008, when dynamic updates are enabled, does not reuse cached DNS responses in all applicable situations, which makes it easier for remote attackers to predict transaction IDs and poison caches by simultaneously sending crafted DNS queries and responses, aka "DNS Server Query Validation Vulnerability."