This indicates an attack attempt to exploit a Denial of Service Vulnerability in Squid Project Squid.
The vulnerability is due to an error in the vulnerable application when handling a maliciously crafted request. A remote attacker may be able to exploit this to cause a denial of service condition on the affected system.
Squid Project Squid 184.108.40.206 to 3.5.28
Squid Project Squid 4.x prior to 4.4
Denial of Service: Remote attackers can crash vulnerable systems.
Apply the most recent upgrade or patch from the vendor: