Upvote:1
It's not quite clear on the maps at the link below, but I'm quite sure, and this appears to be supported by the maps, that there is an airside connection between Terminal 2 and Terminal 3.
https://www.gru.com.br/en/passenger/discover-gru/airport-maps/
So, if you bought your journey as one ticket, and you do not need to collect your luggage, you should not have to go through immigration to get to your connecting flight.
That said, you really should check with the issuing airline.
Edit: I arrived at GRU Terminal 3 yesterday (30/11/2021). There is a connection with Terminal 2, airside. It was guarded, but seemed in operation.