  FT_Stream_Seek( FT_Stream  stream,
                  FT_ULong   pos )
  {
    FT_Error  error = FT_Err_Ok;


    if ( stream->read )
    {
      if ( stream->read( stream, pos, 0, 0 ) )
      {
        FT_ERROR(( "FT_Stream_Seek:"
                   " invalid i/o; pos = 0x%lx, size = 0x%lx\n",
                   pos, stream->size ));

        error = FT_Err_Invalid_Stream_Operation;
      }
    }
    /* note that seeking to the first position after the file is valid */
    else if ( pos > stream->size )
    {
      FT_ERROR(( "FT_Stream_Seek:"
                 " invalid i/o; pos = 0x%lx, size = 0x%lx\n",
                 pos, stream->size ));

      error = FT_Err_Invalid_Stream_Operation;
    }

    if ( !error )
      stream->pos = pos;

    return error;
  }

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.