One of the bigger mistakes of the RIR/Internet Addressing world was allowing non CIDR aligned stuff to exist on v4, all be it that sin was committed a long time ago (and you could argue they knew no better...), but my god it's such a bug magnet.

Huge hate for the fact that you have to support two kinds of IP blocks, a range 1.2.3.4 -> 1.2.3.7 and a CIDR 1.2.3.0/24