Have another circuit on-chip which is more sensitive to glitches than the CPU. Whenever that circuit detects a glitch in the clock, the power supply, the reset

Have another circuit on-chip which is more sensitive to glitches than the CPU. Whenever that circuit detects a glitch in the clock, the power supply, the reset line, electric fields or magnetic fields, it halts the CPU until the whole system is reset. Not very hard to build - I don't know why every chip doesn't include it by default. As well as protecting against deliberate attacks, it would also protect against accidentally running a chip out of spec - for example not having decoupling capacitors on the power supply, causing intermittent behaviour.