GrapheneOS Unable to Complete Pixel 11 Port Due to Cut Security Feature

GrapheneOS has completed a partial port to the new Pixel 11 devices, but they say they're unable to complete it due to Google dropping ARM Memory Tagging Extension (MTE) support.

MTE is a hardware feature in ARM chips that can detect and prevent memory safety violations. It works by assigning a random tag to each location in memory. If memory is accessed but the tags don't match, MTE will detect it as a memory safety violation. Depending on how it's configured, it can crash the program right then and there to stop an exploit early in its tracks.

This is a particularly widespread class of vulnerabilities, making up around 76% of all vulnerabilities in Android at one point according to Google's data. Eliminating memory safety vulnerabilities would mean categorically removing the largest class of vulnerabilities.

Google were the first to ship MTE support in their Pixel phones with the Pixel 8 series of devices. According to Android's documentation, Pixels are still the only Android phones shipping support for MTE even years later.

Apple shipped their own implementation of MTE, calling it Memory Integrity Enforcement, on the iPhone 17 series and Macs with the M5 chip and up.

GrapheneOS considers it such an essential security feature that it's part of their requirements for a device to support GrapheneOS at all.

It's a shame, then, that Google has seemingly dropped the feature they were the first to bring to market. GrapheneOS says they haven't decided what to do about the situation quite yet, but they might have to skip supporting the Pixel 11 series entirely.

GrapheneOS partnered with Motorola to create devices that meet the minimum requirements for GrapheneOS support, however they're not available yet. For now, they're recommending users stick with Pixel 8, 9, and 10 series phones.

The Pixel 11's do ship with security improvements such as the new Titan M3 security chip that supports quantum-safe secure boot, making it all the more baffling that they would cut such an important security feature as MTE.