There is no "lifeboat" capsule on the ISS, the 3 manned spacecraft currently docked (one 4 crew Dragon, one 3 crew Soyuz and the 2 crew Starliner) carried the current occupants up to the station and in normal circumstances would carry the same crew back either on a normal rotation or in an emergency. There are currently nine people on the ISS which as said above is more than planned for an extended time so some shuffling around and a two crew dragon Launch will be needed to get back to 7 assuming they don't use Starliner which is looking increasingly unlikely. There are also 3 cargo spacecraft currently docked. Picture below.
