This indicates an attack attempt against Denial of Service vulnerability exists in Niels Provos libevent.
The vulnerability is due to an error when the vulnerable software handles a maliciously crafted DNS packet. A remote attacker can exploit this to crash the target vulnerable system.
Niels Provos libevent 1.2
Niels Provos libevent 1.2a
Denial of Service: Remote attackers can crash vulnerable systems.
Apply the most recent upgrade or patch from the vendor.