A myriad of common Linux distributions, including Debian,
Ubuntu, RHEL/CentOS, among numerous others use what's known as a "stable" software release model. This involves
freezing packages for a very long time and only ever backporting security fixes that have received a CVE. However, this approach misses the vast majority of security fixes.
Most security fixes do not receive CVEs because either the developer simply doesn’t care or because it’s not obvious whether or not a bug is exploitable at first.