An issue was discovered in Squid before 4.15 and 5.x before 5.0.6. Due to a buffer-management bug, it allows a denial of service. When resolving a request with the urn: scheme, the parser leaks a small amount of memory. However, there is an unspecified attack methodology that can easily trigger a large amount of memory consumption.
https://www.debian.org/security/2021/dsa-4924
https://security.netapp.com/advisory/ntap-20210716-0007/
https://lists.debian.org/debian-lts-announce/2021/06/msg00014.html
https://github.com/squid-cache/squid/security/advisories/GHSA-ch36-9jhx-phm4
https://bugs.squid-cache.org/show_bug.cgi?id=5104