New AMD CPU Vulnerability Might Require Threading To Be Disabled

A newly found SQUIP vulnerability that affects all SMT-enabled CPUs, which includes all Zen processors, can only be dealt with by slowing down the CPU.

9 Years of AMD Processors Vulnerable to 2 New Side-Channel Attacks

AMD has found themselves in a predicament, with all of their Zen processors vulnerable to a medium-security flaw that allows threat actors (hackers) to run attacks that can reveal 4096-bit RSA keys with little difficulty. This vulnerability was discovered by cybersecurity researchers and was further elaborated in a paper entitled SQUIP: Exploiting the Scheduler Queue Contention Side Channel,” which AMD then confirmed to be true.

One of the authors said that “An attacker running on the same host and CPU core as you, could spy on which types of instructions you are executing due to the split-scheduler design on AMD CPUs,” and also explained that “Apple’s M1 (probably also M2) follows the same design but is not affected yet as they haven’t introduced SMT in their CPUs yet.”

There is a fix, but at what cost?

AMD CPUs make use of SMT, simultaneous multithreading, which is a technique that improves the efficiency of superscalar processors and allows multiple threads of execution, using the CPU’s resources efficiently. The vulnerability comes from the way that the processor works by executing more lines of code on a single core so as to boost performance. However, this does allow potential threat actors to observe these instructions provided that they can get malware installed on the device first.

As with most forms of malware, a software patch can solve the issue, and this vulnerability is no exception. However, this fix comes with a major downside. In order to fix this vulnerability, SMT needs to be disabled which will result in a significant performance drop. Amd said the folllowing, “AMD recommends software developers employ existing best practices including constant-time algorithms and avoiding secret-dependent control flows where appropriate to help mitigate this potential vulnerability.”

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