According to the findings, AMD's CPU may have kept "stale quotient data" within its registers even after the patchwork was over, consequently providing attackers with a window to retrieve private information. The original fix was to conduct a final “dummy division 0/1 before returning from the #DE exception handler.” The idea is quite straightforward: after completing the 0/1 division, which always yields zero results, any remaining old data would be eliminated.
The drawback of the fix, explained by Petkov, was that the speculative execution attack would have progressed too far by the time that the security feature took effect. There would already be some outdated data on AMD's divider, which the attackers could access before the dummy division kicked in.
Petkov notes that his new solution now upholds that same division in several scenarios:
"Initially, it was thought that doing an innocuous division in the #DE handler would take care to prevent any leaking of old data from the divider but by the time the fault is raised, the speculation has already advanced too far and such data could already have been used by younger operations,” says Petkov. “Therefore, do the innocuous division on every exit to userspace so that userspace doesn't see any potentially old data from integer divisions in kernel space[…]Do the same before VMRUN too, to protect host data from leaking into the guest too,"
Similar instances indicate how busy this month turned out to be for vulnerabilities in the CPU realm, for both AMD and Intel. From Intel’s severe Downfall vulnerability (affecting Skylake through Tiger Lake/Rocket Lake) to AMD's SQUIP and Inception vulnerabilities and the now re-fixed "divide by zero" vulnerability, researchers have shown much determination in solving the issues.
However, while these new issues are connected to speculative execution vulnerabilities, they still do not come close to the illustrious history of Meltdown and Spectre days. Speculative execution describes how contemporary CPUs attempt to foresee calculation steps before they are even required, ensuring that the essential data is already available in the event that the execution is asked for. Although several of those vulnerabilities' remedies resulted in (often significant) performance costs, it is at least encouraging that AMD's 0/1 dummy division does not have any additional expenses.
Two new vulnerabilities have been found in Intel processors. They are undocumented capabilities of the manufacturer that allow hijacking control over the device. Access to them opens in a special mode that in most cases only Intel engineers have access to. However, in some scenarios it can also be activated by hackers. Information security experts suggest that these options may be present in all current Intel processors and see them as a major potential threat.
According to Positive Technologies experts Mark Yermolov and Dmitry Sklyarov, there are two undocumented instructions in Intel processors that allow modification of the microcode and gain control over the processor and the entire system.
"The discovered instructions allow bypassing all existing x86 architecture protection mechanisms in modern processors," said Yermolov.
The experts specified that the features found are in Intel's Atom processor family, which has been updated since 2011 to the present day.
"In theory, the vulnerabilities found can be exploited by any attacker who has the necessary information", Alexander Bulatov, Commercial Director of RuSIEM, told the publication.
In this case, the hacker would get a whole set of opportunities to control the compromised system.
“This can be either the simplest forced shutdown of the device, or flashing the processor with microcode that secretly performs certain tasks of the attacker,” explained Bulatov.
According to Yermolov, instructions can be activated remotely only in a special mode of operation of processors Red Unlock, which only Intel engineers should have access to. As Positive Technologies noted, some processors have vulnerabilities that allow third parties to enable Red Unlock mode as well.
Intel's press office said it takes Positive Technologies' research seriously and is carefully reviewing their claims.
The vulnerabilities found are potentially dangerous for users of devices based on the Intel Atom family. These are low-power processors mainly used in netbooks, tablets, POS terminals and POS machines.
The stock of Intel Corp was rallied to close in the last minutes of Thursday 21st January 2021 after the unlikely announcement of quarterly results by the chipmaker at the end of the day, but the stock was reversed in prolonged trading as the firm dealt with long-term plans.
One of the biggest computing giants of the world – Intel has utilized the power of technology and has launched four new series of processors in the Consumer Electronics Show 2021. They affirmed the users that these processors would offer a “Premium PC experience” that would also provide some additional and distinct features.