Microsoft ASP.NET Forms suffers from a null byte termination authentication bypass vulnerability that exists in the CopyStringToUnAlingnedBuffer() function of the webengine4.dll library used by the .NET framework. The unicode string length is determined using the lstrlenW function. The lstrlenW function returns the length of the string, in characters not including the terminating null character. If the unicode string containing a null byte is passed, its length is incorrectly calculated, so only characters before the null byte are copied into the buffer.
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