long UnserializeInt(IMkvReader* pReader, long long pos, long long size,
 long long& result_ref) {
 if (!pReader || pos < 0 || size < 1 || size > 8)
 return E_FILE_FORMAT_INVALID;

 signed char first_byte = 0;
 const long status = pReader->Read(pos, 1, (unsigned char*)&first_byte);

 if (status < 0)
 return status;

 unsigned long long result = first_byte;
 ++pos;

 for (long i = 1; i < size; ++i) {
 unsigned char b;

 const long status = pReader->Read(pos, 1, &b);

 if (status < 0)
 return status;

    result <<= 8;
    result |= b;

 ++pos;
 }

  result_ref = static_cast<long long>(result);
 return 0;
}

The product receives input or data, but it does not validate or incorrectly validates that the input has the properties that are required to process the data safely and correctly.