To illustrate the issue with an extreme example, consider that a disused repository on github full of security holes is highly unlikely to have any CVEs regardless of age. The software has to present a worthwhile target (ie have a substantial long term userbase) before anyone will bother to look for exploits. (I guess that might change in the near future thanks to AI but I don't think we're there just yet.)
MaraDNS is a worthwhile target; two people have been auditing it this year, in fact:
https://github.com/samboy/MaraDNS/pull/137
https://github.com/samboy/MaraDNS/security/advisories/GHSA-c...