Microsoft has been rushing to mitigate the Meltdown and Spectre processor vulnerabilities, but it hasn’t been all smooth sailing. The company has confirmed that its KB4056892 update is putting some AMD PCs in an unbootable state, and is halting the roll out as a result.

The fault, according to Microsoft, is with AMD.

“After investigating, Microsoft has determined that some AMD chipsets do not conform to the documentation previously provided to Microsoft to develop the Windows operating system mitigations to protect against the chipset vulnerabilities known as Spectre and Meltdown,” said a spokesperson. “To prevent AMD customers from getting into an unbootable state, Microsoft will temporarily pause sending the following Windows operating system updates to devices with impacted AMD processors at this time.”

For AMD users, it means remaining vulnerable to the chipset flaw for now. However, others are working on temporary solutions to the problem, including Mozilla. The non-profits Firefox browser has adjusted the accuracy of its time sources to make attacks via the browser more difficult.

Meltdown and Spectre Explained

When a command is sent to perform any task, the CPU passes control to the kernel, which stays below the surface in processes even once the CPU takes back control. This is to ensure smoother and faster performance, but also means systems are potentially at risk at kernel level.

Attackers can use JavaScript in the browser to read memory on a users machine, potentially accessing keystrokes and passwords. However, they need to measure precise time intervals to do so, so Mozilla’s fix works as a temporary solution.

For a robust solution, some argue that a complete processor replacement is required, while Intel believes security updates are enough. Microsoft says it’s working with AMD to resolve the issue, so we can expect a working patch soon.

However, it’s worth noting that the bugs don’t affect AMD processors in the same way as Intel. According to the company, only one out of variants of Spectre doesn’t affect it, and Meltdown not at all. Due to this, AMD processors should see no impact on performance.

For those affected by the boot issues, Microsoft has some documentation, but it’s quite basic. In essence, it advises either performing a system restore or uninstalling the updates in safe mode.