AMD Flaws Acknowledged
CTS-Labs published several AMD flaws over a week ago. For those of us who read vulnerability disclosures regularly, this particular disclosure was curious. Not only was the branded website bereft of any real technical details, but it also lacked any type of information about coordination with AMD. The disclosure also had bizarre legal disclaimers, including the following:
“The opinions expressed in this report are not investment advice nor should they be construed as investment advice or any recommendation of any kind.”1
In fact, were it not for Trail of Bits stepping forward and acknowledging they had been paid by CTS-Labs to review and confirm the accuracy of CTS-Labs findings, the whole thing would have been difficult to take seriously.
However, as of this morning, AMD has published a detailed acknowledgement of the CTS-Labs vulnerabilities. Although no patches have been published, we have a much better understanding of the severity of these vulnerabilities and our customers’ exposure.
Vulnerability details
Despite the flashy website and many news articles since the disclosure, our assessment is the AMD vulnerabilities are overhyped and nowhere near the severity of Spectre and Meltdown. Those two flaws were particularly concerning for two reasons. First, they’re based on fundamental flaws in the design of processors. Secondly, those vulnerabilities can be exploited by unauthenticated remote attacks. For example, the Spectre whitepaper specifically mentions a JavaScript proof of concept.
Impact assessment
All the discussed AMD flaws, except CHIMERA-HW, are firmware issues. Patching firmware issues is significantly easier than mitigating a hardware flaw. AMD is likely to push out a firmware fix relatively quickly since we’ve seen it done before. CHIMERA-HW does look like it’s a vulnerability at the hardware level. CTS-Labs is very quick to call this a “Manufacturer Backdoor.” More likely, it’s probably just unintentionally poor design work.
Prevalence
The other part of this vulnerability that needs to be considered is AMD’s prevalence. Meltdown and Spectre were a big deal because they affected a large variety of processors. AMD represents about 20 percent of the CPU market share, and only a subset of that is vulnerable to these vulnerabilities.
(No) Urgently required actions
These vulnerabilities aren’t good, but you probably shouldn’t lose sleep over them either. AMD reported they will provide firmware updates and mitigations “in the upcoming weeks.” That seems about as good as you can ask, given CTS-Labs’ lack of coordination effort.
Tenable is actively researching new plugins to identify these issues. As always, ensuring administrator access is restricted to only the most trusted users will go a long way in protecting everybody from these vulnerabilities.