Come on, since jailbreak discovered (checkm8 as king of it) you can run pretty much anything just on iphone itself including automated tests, fuzzing, debug and crash dump analyses. Break is always easier than build. iMessage plagued with such bugs since 2010, the question is how it is not yet rebuild up to decent quality. Retarded security measures like blastdor or aslr is irrelevant as these mostly a security theatre that just require extra step to avoid.