This indicates an attack attempt on a Denial of Service Vulnerability in ISC BIND.
A remote, unauthenticated attacker can exploit this vulnerability by sending a large number of DNS requests with a large number of edns-key-tag options. Successful exploitation results in the exhaustion of system memory.
ISC BIND 9.10.7 -> 9.10.8-P1
ISC BIND 9.11.3 -> 9.11.5-P1
ISC BIND 9.12.0 -> 9.12.3-P1
Denial of Service: Remote attackers can crash vulnerable systems.
Refer to the vendor supplied advisory for updates: