Security research firm Embedi has recently published a report on the Marvell Avastar Wifi chip used in many devices including Microsoft Surface and Surface Pro, Samsung Chromebooks and some Samsung phones and the Sony Playstation 4 to name but a few.

The flaw in Marvell’s implementation of the ThreadX operating system running on the Wifi chip, allows an attacker to compromise the Wifi chip, then escalate the attack into the operating system of the host device and run arbitrary code.

The Marvell Avastar is a System On a Chip (SoC) device, which for performance reasons, typically sits on the main bus of the parent device. This means it has direct access to the host system’s memory, so a compromise of the Avastar SoC could grant an attacker access to the data stored in the memory of the host device.

Because the Avastar SoC functions independently from the host operating system, as soon as the device is powered on it is vulnerable to this attack – even before the host device’s operating system has booted up.

According to the report’s author:

This vulnerability can be triggered without user interaction during the scanning for available networks. This procedure is launched every 5 minutes regardless of a device being connected to some Wi-Fi network or not. That’s why this bug is so cool and provides an opportunity to exploit devices literally with zero-click interaction at any state of wireless connection (even when a device isn’t connected to any network). For example, one can do RCE in just powered-on Samsung Chromebook. So just to summarize:

• It doesn’t require any user interaction.
• It can be triggered every 5 minutes in case of GNU/Linux operating system.
• It doesn’t require the knowledge of a Wi-Fi network name or passphrase/key.
• It can be triggered even when a device isn’t connected to any Wi-Fi network, just powered on.

In the proof of concept detailed in the report, the researchers used a Valve Steamlink gaming console which runs a Linux operating system and were able to compromise the device and inject arbitrary messages into the kernel log on the host device.

The detailed report and explanation of the proof of concept escalation attack can be found here: https://embedi.org/blog/remotely-compromise-devices-by-using-bugs-in-marvell-avastar-wi-fi-from-zero-knowledge-to-zero-click-rce/