AMD confirms it has CPU vulnerabilities akin to Meltdown and Spectre

AMD has disclosed a new class of security vulnerabilities in its CPUs, which the company has addressed in a new technical paper outlining strategies to mitigate the vulnerabilities that affect AMD Ryzen, Threadripper, Athlon, Instinct, and EPYC CPUs.

2

The vulnerabilities have been dubbed Transient Scheduler Attack (TSA), which is a type of attack that doesn't attack the software directly but instead leaks information by observing the hardware's behavior, such as how long it takes the hardware to complete a certain task. These are called side-channel attacks.

TSA is similar to infamous security vulnerabilities such as Meltdown and Spectre, which exploited how CPUs optimize performance using a technique called speculative execution, which involves the CPU predicting what instructions it might need next and starting to execute them before it's sure they are actually required.

If the CPU guesses correctly, efficiency is increased, while if it guesses wrong, the results are discarded. This, wherein lies the security problem that led to Meltdown and Spectre, as it was discovered that even discarded speculative operations can leave traces in the CPU's cache, which can be probed by attacks and result in sensitive data such as passwords or encryption keys being leaked.

Similar to Meltdown and Spectre, the new TSA exploits "false completions," which is when the CPU thinks it has completed a task, but hasn't, resulting in it acting on incorrect data. The exploit lies within measuring the timing differences of this faulty behavior, enabling an attack to infer sensitive data such as OS kernel memory, other apps, and CPU internal states.

AMD explains that for a TSA attack to be pulled off, an attacker must already have local access to a device and be capable of running arbitrary code. This security vulnerability isn't exploitable through a website or remotely.

Affected AMD CPUs

• AMD EPYC (3rd Gen "Milan" and 4th Gen "Genoa" server chips)
• AMD Ryzen (Desktop and Mobile processors, Zen 2 (some models), Zen 3 and Zen 4 generations)
• AMD Threadripper (High-end desktop/workstation chips)
• AMD Athlon (Some newer models)
• AMD Instinct (Data center GPUs with compute cores)

For a full list of affected CPUs, check out the AMD website here.