This indicates an attack attempt to exploit a Buffer Overflow Vulnerability in Squid Project Squid.
A remote attacker can exploit this vulnerability by sending a crafted request to the target server. Successful exploitation will result in the attacker being able to execute arbitrary code with the privileges of the server while an unsuccessful attack will cause the server process to abnormally terminate.
Squid Project Squid 4.x through 4.7
System Compromise: Remote attackers can gain control of vulnerable systems.
Apply the most recent upgrade or patch from the vendor.