The CPU as a Weakness: how to Manage Hardware Risks with Confidence

Vulnerabilities in IT environments appear in different forms. The most common ones are likely software vulnerabilities that have not been patched. Then there are weak passwords, misconfigurations or network switches that have been EOL for five years. However, another type of security gap sometimes causes significant confusion during the scans: hardware vulnerabilities.

We have become accustomed to the continuous emergence of software vulnerabilities, and hopefully, it is now standard practice for every company to regularly scan its network for vulnerabilities and apply patches. Unfortunately, mistakes are not limited to software developers – CPU developers are not immune either. CPU vulnerabilities often arise from design flaws, allowing malicious actors to exploit unintended side effects to access sensitive data. Unlike software vulnerabilities, which can often be resolved through patches or updates, hardware vulnerabilities require either microcode updates or fundamental architectural changes in future processor designs.

Microcode Updates

The only way to mitigate CPU vulnerabilities is by applying microcode updates, which are typically distributed through the operating system or sometimes even through firmware (UEFI/BIOS). Microcode is a low-level software layer within the processor that translates higher-level machine instructions into specific internal operations.

While end users do not traditionally update microcode themselves, manufacturers like Intel provide relevant updates to patch certain vulnerabilities without requiring a full hardware replacement. However, these updates often introduce performance loss, as they disable or modify certain CPU optimizations to prevent exploitation. In some cases, this can even lead to performance reductions of up to 50%.

Flaws on different levels

Since these vulnerabilities exist at the CPU level, tools like the Greenbone Enterprise Appliance detect and report them. However, this can lead to misconceptions, as users might mistakenly believe that the reported vulnerabilities originate from the operating system. It is crucial to understand that these are not OS vulnerabilities; rather, they are architectural flaws in the processor itself. The vulnerabilities are detected by checking for the absence of appropriate microcode patches when an affected CPU is identified. For example, if a scan detects a system that lacks Intel’s microcode update for Downfall, it will be reported as vulnerable. However, this does not mean that the OS itself is insecure or compromised.

Performance or safety?

In the end, mitigating CPU vulnerabilities always involves trade-offs, and users must decide which approach best suits their needs. In principle, there are three options to choose from:

• Apply microcode updates and accept significant performance degradation in compute-heavy workloads.
• Forego certain microcode updates and accept the risks if the probability of exploitation is low in their environment.
• Replace the affected hardware with CPUs that are not vulnerable to these issues.

Ultimately, the decision depends on the specific use case and risk tolerance of the organization or individual responsibles.