AMD's Zen 3 CPU architecture may contain a feature that hackers could exploit for side-channel attacks such as Spectre, according to AMD itself.

A speculative execution feature common in modern processors is known as Predictive Store Forwarding (PSF) in Zen 3. Basically, this feature uses a branch prediction algorithm to guess which instructions are likely to be sent next, and then fetches those instructions ahead of time. The point is to accelerate the performance pipeline within the microprocessor, but as TechPowerUp reports, this feature comes with risks.

If a misprediction occurs, software like web browsers that use "sandboxing" can put the CPU at risk of side-channel attacks. Just a few ticks, but that's all it takes.

Sandboxing (quarantine) is actually designed to prevent threats by putting suspect code in a naughty step and questioning its motives. However, as with the Spectre vulnerability we previously reported on, the possibility of cache state changes in such cases could allow hackers to access chunks of personal data.

Web browsers tend to rely less on isolation processing these days due to the Spectre and Meltdown vulnerabilities, but the risks that AMD candidly outlines still exist; a paper published by AMD states this in the header of their security analysis:

"Security concerns arise when there is code that implements some security control that can be bypassed when the CPU makes an unauthorized guess. This can occur when a program (such as a web browser) hosts untrusted pieces of code and the untrusted code can influence how the CPU makes guesses in other areas in a way that can lead to data leakage.

If an attacker is able to execute code within the target application, it may be possible to influence the speculation of other loads within the same application by intentionally training the PSF predictor with malicious information.

However, there are safe ways to address possible vulnerabilities by simply turning off PSF.

AMD does not recommend this as an option because it can degrade performance; Intel's Meltdown and Spectre mitigations on their CPUs also led to similar performance limitations in some cases.

Surprisingly, however, tests (via Phronix) show that turning this feature off only reduces CPU performance by 1%.

If you are concerned, turning it off may be your best option for now.

A short-term fix for those currently affected may come in the form of a firmware update, but a longer-term solution will likely have to come in the form of changes to the architecture itself. In previous such exploits, the concern was mostly from large server providers who did not want to leave security holes unpatched.