Just refoamed a woofer and need to reattach the gasket, what glue?

PVA/Elmer´s/carpenter´s glue works fine.

Only "problem" is that it´s not tacky (the way contact/neoprene cement is) so you have to clamp it down in place for an hour or two.
You can use the cabinet itself for that, put it face up on a carpet or wooden floor and the speaker on its own cutout, face down, so gasket lies flat and tight between them, speaker own weight is enough, no need for screws or clamps.