XACK DNS 1.11.0 to 1.11.4, 1.10.0 to 1.10.8, 1.8.0 to 1.8.23, 1.7.0 to 1.7.18, and versions before 1.7.0 allow remote attackers to cause a denial of service condition resulting in degradation of the recursive resolver's performance or compromising the recursive resolver as a reflector in a reflection attack.