More information about this security flaw is available in the following bug: https://bugzilla.redhat.com/show_bug.cgi?id=2325340 Disclaimer: Community trackers are created by Red Hat Product Security team on a best effort basis. Package maintainers are required to ascertain if the flaw indeed affects their package, before starting the update process.
This is already fixed in F41. Not nearly important enough to fix in F40. (Apologies to any F40 users using a socks4a proxy with both a username of exactly 255 bytes and also a hostname of exactly 255 bytes. :)