Millions of AMD CPUs found vulnerable to 18-year-old 'Sinkclose' deep-system flaw but it's pretty difficult to exploit

HardwareProcessorsMillions of AMD CPUs found vulnerable to 18-year-old ‘Sinkclose’ deep-system flaw but it’s pretty difficult to exploitWhen you purchase through links on our site, we may earn an affiliate commission.Here’s how it works.

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A photo of three AMD Ryzen processors resting on a metal heatsink

Security researchers have discovered a vulnerability that affects almost all AMD CPUs, allowing access to some of the deepest parts of the chip. Named ‘Sinkclose’, the flaw allows attackers that already have kernel-level access to modify SMM (System Management Mode) settings even with existing protections enabled.

Attackers could use the flaw to install malware that would be virtually undetectable, and extremely difficult to remove. However, gaining kernel access in the first place is no easy task, and AMD has already begun releasing fixes for some of the affected chips (viaBleeping Computer).

Exploiting the flaw would require attackers to first establish kernel access on a target machine via a different attack method. This level of system access is defined as aRing 0 privilegeand essentially opens up the heart of the system to further attack. If successful, an attacker could then enable Ring -2 privileges to install an undetectable bootkit that compromises the master boot record, meaning that even an OS reinstall would be unable to remove it.

AMD has releasedan advisory noticedetailing chips vulnerable to the attack, along with firmware fixes that are being provided to OEMs for BIOS updates to fix the flaw. However, Ryzen 3000, 2000 and 1000 series chips will not receive updates, as AMD told Tom’s Hardware that"there are some older products that are outside our software support window."

Many of AMD’s most recent processors have already received updates to remove the vulnerability. It’s worth noting that while Kernel-level system access is very difficult to achieve for a would-be-attacker, it’s not impossible—so if you own an AMD CPU and haven’t updated the BIOS in a while, it’d be worth checking with your motherboard manufacturer to make sure you’re completely up-to-date.

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Still, it’s data center systems and machines holding very sensitive information that would likely be the targets here, so home users shouldn’t be too concerned.

AMD’s latest Zen 5 9000 series processors like theRyzen 5 9600XandRyzen 7 9700Xare not included on the list, presumably as they’re using the latest BIOS revisions with the fix already applied. While this flaw might be difficult to leverage, it’s still a pretty nasty way for a system to fall prone to malicious actors, so the usual advice applies—keep your BIOS up-to-date, and your antivirus in tip-top condition to prevent attacks in the first place.

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