A 0-click exploit chain for the Pixel 9 (Project Zero)
Over the past few years, several AI-powered features have been added to mobile phones that allow users to better search and understand their messages. One effect of this change is increased 0-click attack surface, as efficient analysis often requires message media to be decoded before the message is opened by the user. One such feature is audio transcription. Incoming SMS and RCS audio attachments received by Google Messages are now automatically decoded with no user interaction. As a result, audio decoders are now in the 0-click attack surface of most Android phones.
The blog entry does not question the wisdom of directly exposing audio decoders to external attackers, but it does provide a lot of detail showing how it can go wrong. The first part looks at compromising the codec; part two extends the exploit to the kernel, and part three looks at the implications:
It is alarming that it took 139 days for a vulnerability exploitable in a 0-click context to get patched on any Android device, and it took Pixel 54 days longer. The vulnerability was public for 82 days before it was patched by Pixel.