
< 	dec->numtiles = dec->numhtiles * dec->numvtiles;
---
> 	uint64_t tmp = (uint64_t)dec->numhtiles * (uint64_t)dec->numvtiles;
> 	if (tmp > SIZE_MAX) {
> 		return JPC_FAILURE; // Or appropriate error handling
> 	}
> 	dec->numtiles = (size_t)tmp;
