squid3 is vulnerable to HTTP Request Injection. The vulnerability exists through special characters in the decoded UserInfo, which is prepended in the absolute URLs, when it checks its cache to see if it can serve up a response on request by making a MD5 hash of the absolute URL of the request.
www.squid-cache.org/Versions/v4/
www.squid-cache.org/Versions/v4/changesets/
github.com/squid-cache/squid/commits/v4
gitlab.com/jeriko.one/security/-/blob/master/squid/CVEs/CVE-2019-12520.txt
lists.debian.org/debian-lts-announce/2020/07/msg00009.html
security.netapp.com/advisory/ntap-20210205-0006/
usn.ubuntu.com/4446-1/
www.debian.org/security/2020/dsa-4682