More information about this security flaw is available in the following bug: https://bugzilla.redhat.com/show_bug.cgi?id=2326335 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.
Fedora 39 is so close to being EOL that submitting an update now would be futile - it would not land in "stable" repositories before EOL. Additionally, this issue has no actual impact in Fedora, because no applications yet use the the zlib-rs feature of rustls and rustls is the only dependent package of zlib-rs.