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STATUS_ILLEGAL_INSTRUCTION
Execution reached an unsupported or invalid instruction encoding
This exception can mean that the byte sequence is not a valid instruction for the active architecture or that it requires a processor feature unavailable on the machine. It can also be a secondary effect of control-flow corruption: a damaged return address or function pointer may branch into data, the middle of another instruction, or an unloaded code region.
Begin with the exact bytes and module mapping at the instruction pointer. If the instruction is valid on newer CPUs, compare deployment feature checks with the compiler target and dispatch logic. If the bytes do not match the on-disk image, investigate patching, memory corruption, or self-modifying/JIT code before replacing the executable.
What to inspect
- Disassemble from a known instruction boundary and preserve the raw bytes.
- Confirm that the address belongs to committed executable memory and the expected module.
- Check CPU feature detection for AVX, AVX-512, or other optional instruction sets.
- Compare in-memory code with symbols and the deployed binary before reinstalling anything.
References
- Microsoft Learn: EXCEPTION_RECORD
- Microsoft Learn: Exception Dispatching
- Microsoft Learn: Specific Exceptions
- Microsoft Windows SDK metadata: ntstatus.h
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