This indicates an attempt to exploit a Denial of Service vulnerability in PowerDNS.
The vulnerability is due to an error in the vulnerable application when handling crafted DNS queries, leading to an out-of-bounds read. A remote attacker may be able to exploit this to cause a denial of service condition on the affected system.
PowerDNS PowerDNS Recursor 4.1.x prior to 4.1.8
Denial of Service: Remote attackers can crash vulnerable systems.
Refer to the vendor's advisory for updates: