Squid before 4.4, when SNMP is enabled, allows a denial of service (Memory Leak) via an SNMP packet.
https://usn.ubuntu.com/4059-1/
https://lists.debian.org/debian-lts-announce/2020/07/msg00009.html
https://lists.debian.org/debian-lts-announce/2018/11/msg00032.html