Without knowing Oracle's approach, this sort of problem is no different from any other software, even tho it reaches a larger scale.

Branch from master, and rerun tests before the final merge, like you should in any other software? (Many processes fail that criterion, see https://bors.tech/ for something that gets this right).

Ideally you work on a different enough bug that there's limited interaction, and ideally that's figured out before you fix it, but those criteria are indeed harder to satisfy in a bigger software.