bool Match(IMkvReader* pReader, long long& pos, unsigned long expected_id,
 unsigned char*& buf, size_t& buflen) {
 if (!pReader || pos < 0)
 return false;

 long long total = 0;
 long long available = 0;

 long status = pReader->Length(&total, &available);
 if (status < 0 || (total >= 0 && available > total))
 return false;

 long len = 0;
 const long long id = ReadID(pReader, pos, len);
 if (id < 0 || (available - pos) > len)
 return false;

 if (static_cast<unsigned long>(id) != expected_id)
 return false;

  pos += len; // consume id

 const long long size = ReadUInt(pReader, pos, len);
 if (size < 0 || len <= 0 || len > 8 || (available - pos) > len)
 return false;

 unsigned long long rollover_check =
 static_cast<unsigned long long>(pos) + len;
 if (rollover_check > LONG_LONG_MAX)
 return false;

  pos += len; // consume length of size of payload

  rollover_check = static_cast<unsigned long long>(pos) + size;
 if (rollover_check > LONG_LONG_MAX)
 return false;

 if ((pos + size) > available)
 return false;

 if (size >= LONG_MAX)
 return false;

 const long buflen_ = static_cast<long>(size);

  buf = SafeArrayAlloc<unsigned char>(1, buflen_);
 if (!buf)
 return false;

  status = pReader->Read(pos, buflen_, buf);
 if (status != 0)
 return false;

  buflen = buflen_;

  pos += size; // consume size of payload
 return true;
}

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.