A single ultra‑long instruction can hijack System Management Mode on x86
Researchers demonstrate a new SMM attack that uses an absurdly long instruction to keep one core busy while the other tries to enter System Management Mode. Because SMM requires all cores to be synchronized, the busy core blocks entry, letting the attacker stay out of SMM and gain control. The proof‑of‑concept shows a hardware‑level attack vector on every x86 CPU.