myMethod

x := 1.  self becomeForward: y.  x := 5.

in the above, x is an instance variable of receiver. If become primitive turns receiver oop into forwarding corpse, now we have a problem that after returning back to given method, a bytecode will attempt to write new ivar value at old location, instead of a new one, since receiver reference are not updated and still points to old object memory location.

The code above crashing Squeak VM (and i guess Cog as well).

I wonder, what security measures can be added to VM in order to prevent it from crashing or corrupting the object memory.

The problem is that at any moment, a receiver's identity could change (it could be due to use of become either in some nested message sends, or even in higher priority process, which interrupted a current one), and after activating the context back, we have a real problem, because there is no range/format checking for receiver, to make sure that it is safe to continue run given compiled method.