This BlackHat talk from 2021 seems relevant: https://i.blackhat.com/USA21/Wednesday-Handouts/us-21-Over-T...
It’s (probably) not the same bug, but gives you an idea of the state of baseband security and the attack surface. The baseband is an ARM chip running an RTOS.
The security situation is not pretty. We have here an XML parser running in the baseband RTOS which has a stack overflow bug. There are no stack canaries and it looks like there’s no ASLR or even NX so they get trivial shellcode execution. Although they didn’t demonstrate persistence or AP compromise, I can’t imagine either of those would be hard from the privileged baseband, especially if the baseband drivers are as bad as the baseband firmware seems to be.