bool CuePoint::TrackPosition::Parse(IMkvReader* pReader, long long start_,
 long long size_) {
 const long long stop = start_ + size_;
 long long pos = start_;

  m_track = -1;
  m_pos = -1;
  m_block = 1; // default

 while (pos < stop) {
 long len;

 const long long id = ReadID(pReader, pos, len);
 if ((id < 0) || ((pos + len) > stop)) {
 return false;
 }

    pos += len; // consume ID

 const long long size = ReadUInt(pReader, pos, len);
 if ((size < 0) || ((pos + len) > stop)) {
 return false;
 }

    pos += len; // consume Size field
 if ((pos + size) > stop) {
 return false;
 }

 if (id == 0x77) // CueTrack ID
      m_track = UnserializeUInt(pReader, pos, size);

 else if (id == 0x71) // CueClusterPos ID
      m_pos = UnserializeUInt(pReader, pos, size);

 else if (id == 0x1378) // CueBlockNumber
      m_block = UnserializeUInt(pReader, pos, size);

    pos += size; // consume payload
 }

 if ((m_pos < 0) || (m_track <= 0)) {
 return false;
 }

 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.