Race condition in the msxml3 module in Microsoft XML Core Services 3.0 as used in Internet Explorer 6 and other applications allows remote attackers to execute arbitrary code or cause a denial of service (application crash) via many nested tags in an XML document in an IFRAME when synchronous document rendering is frequently disrupted with asynchronous events as demonstrated using a JavaScript timer which can trigger NULL pointer dereferences or memory corruption aka \MSXML Memory Corruption Vulnerability.\