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Pork Explosion Android flaw: How is it used to create a backdoor?

The Pork Explosion vulnerability present in some Foxconn-created app bootloaders can be used to create an Android backdoor. Expert Nick Lewis explains how the flaw works.

A vulnerability called Pork Explosion with the ability to create an Android backdoor was found in the app bootloader from device manufacturer Foxconn. While the scope of the devices is small, the vulnerability may have serious risks. What does the app bootloader do in this case, and how is the backdoor created?

The information security industry continues to satirize itself with the Pork Explosion Android vulnerability. Researcher Jon Sawyer found a vulnerability in InFocus and Nextbit smartphones that was introduced by Foxconn during the building and assembly of the devices.

The backdoor was created during Foxconn's design and manufacturing process and appears to be part of the debugging environment used to troubleshoot the device when it was still in development. Including a debug environment is necessary, but it is typically disabled prior to mass production to help protect the security of the device.

The Pork Explosion Android vulnerability allows an attacker to connect via USB to gain unrestricted root shell access via the app bootloader when booting. The bootloader performs the basic task of hardware initialization and loads the Linux kernel. During this time, the kernel protections are not available.

The risk from this vulnerability is high for physical access to vulnerable devices, but since these devices are not as widely deployed as those made by Samsung or other major manufacturers, the overall risk is low.

Nextbit remediated the Android vulnerability by removing the file system used in the debug environment.

Enterprises that contract out device or component manufacturing may want to check their supply chains to determine if they have been exposed to vulnerabilities similar to Pork Explosion. If so, those enterprises may want to ensure they have integrated security into their supply chains to prevent vulnerabilities from being introduced that way.

Enterprises may also want to ensure any third parties in their supply chain are responsible for any vulnerabilities they introduce into a device, since the enterprise might not be able to fix the vulnerability themselves.

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