Two Hidden Instructions Discovered in Intel CPUs Enable Microcode Modification .
Security researchers Mark Ermolov, Dmitry Sklyarov, and Maxim Goryachy discovered two undocumented x86 instructions that can be used to modify the CPU microcode. The instructions can only be executed when the CPU runs in debug mode, which makes them not easily exploitable, though.
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Why does Intel keep having and adding so so so very many instructions that are undocumented in every form… It’s so horrible from a security standpoint (hence why so many theories that a lot of these are for exploitations) and it just complicates the chips even further. We need everything to switch to RISC-V or something, and keep it to the spec… >.>
AMD does also do the same because they have to stay compatible with Intel. Now thankfully they don’t go way way crazy extreme with it like intel does, but they have had to implement a certain subset of the functionality just to work. However, so far as far as I’ve heard there hasn’t been any big exploits of their stuff like there has been for Intel, repeatedly.