Security research firm Paradigm Shift this week published details of a new BootROM vulnerability affecting Apple’s A12 and A13 chips. The firm also provided a working proof-of-concept exploit named “usbliter8.”
Unfortunately, whil Apple has in the past been able to patch discovered security flaws in their devices, it is impossible to do so in this case, as the BootROM (also known as SecureROM) is the first code run by an iPhone when it powers on, and that code is baked into the chip, meaning a software patch cannot fix it.
The Paradigm Shift team discovered the issue in Apple’s A12 and A13 SoCs. Those chips were used in the iPhone XS, iPhone XS Max, iPhone XR, iPhone 11, iPhone 11 Pro, iPhone 11 Pro Max, and the second-generation iPhone SE model released in early 2020.
The exploit takes advantage of a bug in the USB controller built into Apple’s chips. When an iPhone receives USB data during startup, the controller uses a memory buffer to store incoming packets. By sending a specific sequence of unusually small packets, bad actors could manipulate an internal hardware pointer in a way that causes it to walk backwards through memory. This allows data to be written to locations it should be unable to reach. The bug appears to be in the USB controller hardware itself, not in Apple’s software.
On A12 devices, the flaw’s exploitation is relatively straightforward, while on A13 devices, exploitation is a bit more difficult, due to Apple introducing a security feature called Pointer Authentication Codes (PAC), which detects and blocks certain types of memory tampering. Paradigm Shift says that while the hack is possible on the A13, it required a lengthy multi-step process before the researchers could take control of the processor.
Once in place, the exploit installs a custom handler that temporarily lowers the device’s security settings, and booting unsigned software without any verification checks.
So, should the average owner of these older iPhones be concerned that their device will be taken over any day now? It’s not likely, as this particular vulnerability has a very narrow and specific attack vector.
Bad guys can’t use this security flaw to hack your iPhone remotely over Wi-Fi or cellular networks, it instes requires the attacker to have a physical USB connection to the device to inject the malicious code.
All users will want to practice safe charging and syncing, not plugging their iPhone into random computers, USB outlets, and chargers, and such. Meanwhile, the flaw will likely be mostly used by law enforcement to crack criminal’s devices or by those three letter government-run “alphabet” agencies we all know are spying on us all.
