An issue has been found in PowerDNS Recursor prior to 4.3.1 and 4.2.2. An issue in the DNS protocol has been found that allow malicious parties to use recursive DNS services to attack third party authoritative name servers. The attack uses a crafted reply by an authoritative name server to amplify the resulting traffic between the recursive and other authoritative name servers. Both types of service can suffer degraded performance as an effect. The effect was already limited in PowerDNS Recursor because of existing mitigations, but additional mitigations relative to this specific attack have been added.