This indicates an attempt to exploit a Denial of Service vulnerability in PowerDNS.
The vulnerability is due to an error when the vulnerable software handles a crafted DNS query. A remote attacker may be able to exploit this to cause a denial of service condition on the affected system.
PowerDNS PowerDNS Recursor prior to 3.6.2
PowerDNS PowerDNS Recursor prior to 3.7.1
PowerDNS PowerDNS Authoritative Server prior to 3.3.1
PowerDNS PowerDNS Authoritative Server prior to 3.4.3
Denial of Service: Remote attackers can crash vulnerable systems.
Apply the most recent upgrade or patch from the vendor.