> Then all someone has to do is generate images that collide

If the hashes are cryptographic, then this is impossible (given today's technology).

> with the ones in the CSAM hash database

The CSAM hash database isn't public AFAIK.

> I remember someone posting about a year ago a bunch of strange looking images that produced those collisions.

You're probably thinking about their proposed 'perceptive hash', which has since been scrapped.