static int fetch_message(char *line, void *file)
{
  FILE *f = (FILE *) file;

  fputs(line, f);
  if (fputc('\n', f) == EOF)
    return -1;

  return 0;
}

The product uses external input to construct a pathname that is intended to identify a file or directory that is located underneath a restricted parent directory, but the product does not properly neutralize special elements within the pathname that can cause the pathname to resolve to a location that is outside of the restricted directory.