Fire Separation Wall - what should I use to seal small exposed openings?
Firestop - caulking or foam (there are other brands of both, just examples, not recommendations.)
These are helpful because they will seal around a cable as it melts in a fire (they expand with exposure to heat/flame) but the majority of the hole could also be addressed with plain old drywall compound (it seals all the other holes in the wall.) Using firestop around penetrations (such as the cable itself) is good practice, and some jurisdictions require more extensive approaches, such as an extended collar with fire sealant around cables, pipes and ducts.