In context: Unpatchable, hardware-level vulnerabilities caused a stir some years ago when they repeatedly turned up in AMD and Intel processors, but they’ve been far rarer on Apple chips. This latest discovery only affects older iPhone processors, but it still shows that even relatively recent SecureROM implementations aren’t foolproof.
Security researchers at Paradigm Shift have published the first iPhone bootROM exploit in years. The process, called usbliter8, targets a hardware-level flaw, which means upgrading to newer hardware is the only real fix.
The exploit affects the iPhone XS’s A12 chip, the Apple Watch Series 4’s S4 chip, and the iPhone 11’s A13 SoC. The S5, found in the Apple Watch Series 5, first-generation SE, and HomePod mini, is vulnerable too. Pulling it off requires physical access and a Raspberry Pi, since the flaw sits in a part of the USB controller that standard Mac and PC USB stacks can’t reach.
A12 and A13 are exposed because of how their USB controllers mishandle data packets, leaving SRAM data insecure. Earlier SoCs avoid the issue because they reset the DMA address after each packet comes through the USB controller, and A14 and newer are also safe, having corrected the underlying configuration.
Using the exploit to jailbreak devices is fairly simple on A12, S4, and S5 chips. A13 is trickier, since SecureROM’s PAC protections add extra steps, but it’s ultimately just as vulnerable as its predecessor. The flaw can’t be patched via software, and altered firmware survives reboots.
While most devices built on these chips have been considered obsolete for years, the iPhone 11 which still runs on the A13 chip happens to be the oldest iPhone that supports iOS 26. Apple isn’t dropping it for iOS 27 this fall, either, so it’s guaranteed at least another year of software updates.
The last unpatchable iPhone jailbreak, checkm8, surfaced in 2019 and covered the A5 (iPhone 4S) through A11 (iPhone X). It later resurfaced as a way to bypass the security chips on some Macs. Together, the two exploits leave every iPhone from the 4S through the 11 open to an unpatchable jailbreak.
A fundamentally similar bootROM exploit recently surfaced for Microsoft’s Xbox One, a console long considered unhackable. But getting it to work proved far harder than on iPhones, requiring a voltage-based hijack to pull off.
