Unpatchable BootROM Flaw in iPhone A12/A13 Enables USB-Based Exploitation

Security researchers have detailed a BootROM vulnerability, usbliter8, affecting Apple's A12 and A13 chips that can be exploited via a specific USB sequence at startup to gain code execution and boot unsigned software; because BootROM resides in hardware, software updates cannot patch it, leaving affected devices vulnerable for life. A12 is easier to exploit, A13 requires bypassing PAC, A11 is unaffected and A14+ are safe; Apple was notified and a full PoC was published.