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MS11-044: JIT compiler issue in .NET Framework
Today we have released MS11-044 to address CVE-2011-1271, a remote code execution vulnerability in the .NET framework. Here we would like to provide more technical information about this vulnerability and why we believe this issue to be unlikely to be exploited. This root cause of CVE-2011-1271 is that there was a bug in the JIT compiler which would cause it to mistakenly determine that a given object is always null (or non-null) and would omit certain checks.