png_write_chunk_data(png_structp png_ptr, png_bytep data, png_size_t length)
{
   /* Write the data, and run the CRC over it */
   if (png_ptr == NULL)
      return;
   if (data != NULL && length > 0)
   {
      png_write_data(png_ptr, data, length);
      /* Update the CRC after writing the data,
       * in case that the user I/O routine alters it.
       */
      png_calculate_crc(png_ptr, data, length);
   }
}

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.