A PUK code for a SIM card, which stands for Personal Unblocking Key, is an eight-digit code that enables a blocked SIM card to be unlocked.

PUK is the code required to unlock a GSM SIM card that has disabled itself after an incorrect PIN code was entered 3-5 times in a row. If an incorrect PUK code is entered a certain number of times ...

The attacker could just swap the SIM in the victim’s device, and perform the exploit with a SIM card that had a PIN lock and for which the attacker knew the correct PUK code.