An issue was discovered in Squid 4.x before 4.15 and 5.x before 5.0.6. If a remote server sends a certain response header over HTTP or HTTPS, there is a denial of service. This header can plausibly occur in benign network traffic.
https://www.debian.org/security/2021/dsa-4924
https://github.com/squid-cache/squid/security/advisories/GHSA-jjq6-mh2h-g39h
https://github.com/squid-cache/squid/commit/051824924c709bd6162a378f746fb859454c674e