Thunderspy Is A New Vulnerability Affecting Thunderbolt Security

Thunderspy is a class of seven vulnerabilities found within Intel's Thunderbolt 3 hardware and the researchers having found nine realistic scenarios for exploiting these Thunderbolt issues across platforms.

The seven Thunderbolt vulnerabilities being disclosed to date include:

Inadequate firmware verification schemes
Weak device authentication scheme
Use of unauthenticated device metadata
Downgrade attack using backwards compatibility
Use of unauthenticated controller configurations
SPI flash interface deficiencies
No Thunderbolt security on Boot Camp

Researcher Björn Ruytenberg summed up the situation as:

These vulnerabilities lead to nine practical exploitation scenarios. In an evil maid threat model and varying Security Levels, we demonstrate the ability to create arbitrary Thunderbolt device identities, clone user-authorized Thunderbolt devices, and finally obtain PCIe connectivity to perform DMA attacks. In addition, we show unauthenticated overriding of Security Level configurations, including the ability to disable Thunderbolt security entirely, and restoring Thunderbolt connectivity if the system is restricted to exclusively passing through USB and/or DisplayPort. We conclude with demonstrating the ability to permanently disable Thunderbolt security and block all future firmware updates.

All Thunderbolt-equipped systems shipped between 2011-2020 are vulnerable. Some systems providing Kernel DMA Protection, shipping since 2019, are partially vulnerable. The Thunderspy vulnerabilities cannot be fixed in software, impact future standards such as USB 4 and Thunderbolt 4, and will require a silicon redesign. Users are therefore strongly encouraged to determine whether they are affected using Spycheck, a free and open-source tool we have developed that verifies whether their systems are vulnerable to Thunderspy. If it is found to be vulnerable, Spycheck will guide users to recommendations on how to help protect their system.

As for mitigating Thunderspy, only systems with Kernel DMA Protection can offer some level of protection. It is reported that Intel isn't able to provide further mitigation against Thunderspy without re-engineered hardware. With Thunderspy, however, physical access to the system is at least required to exploit.

More details on Thunderspy at thunderspy.io.

Update: Intel has published their guidance on the matter here.