An issue was discovered in Squid before 4.10. Due to incorrect input validation, it can interpret crafted HTTP requests in unexpected ways to access server resources prohibited by earlier security filters.
https://www.debian.org/security/2020/dsa-4682
https://usn.ubuntu.com/4289-1/
https://security.netapp.com/advisory/ntap-20210304-0002/
https://security.gentoo.org/glsa/202003-34
https://lists.debian.org/debian-lts-announce/2020/07/msg00009.html
http://www.squid-cache.org/Versions/v4/changesets/SQUID-2020_1.patch
http://www.squid-cache.org/Versions/v3/3.5/changesets/SQUID-2020_1.patch
http://www.squid-cache.org/Advisories/SQUID-2020_1.txt
http://lists.opensuse.org/opensuse-security-announce/2020-05/msg00010.html
http://lists.opensuse.org/opensuse-security-announce/2020-03/msg00012.html