extract_initial_length_and_fourcc (guint8 * data, guint64 * plength,
    guint32 * pfourcc)
{
  guint64 length;
  guint32 fourcc;

  length = QT_UINT32 (data);
  GST_DEBUG ("length %08" G_GINT64_MODIFIER "x", length);
  fourcc = QT_FOURCC (data + 4);
  GST_DEBUG ("atom type %" GST_FOURCC_FORMAT, GST_FOURCC_ARGS (fourcc));

  if (length == 0) {
    length = G_MAXUINT32;
  } else if (length == 1) {
    /* this means we have an extended size, which is the 64 bit value of
     * the next 8 bytes */
    length = QT_UINT64 (data + 8);
    GST_DEBUG ("length %08llx", length);
  }

  if (plength)
    *plength = length;
  if (pfourcc)
    *pfourcc = fourcc;
}

The product performs operations on a memory buffer, but it reads from or writes to a memory location outside the buffer's intended boundary. This may result in read or write operations on unexpected memory locations that could be linked to other variables, data structures, or internal program data.