 MagickExport int LocaleUppercase(const int c)
 {
  if (c == EOF)
     return(c);
 #if defined(MAGICKCORE_LOCALE_SUPPORT)
   if (c_locale != (locale_t) NULL)
    return(toupper_l((int) ((unsigned char) c),c_locale));
#endif
  return(toupper((int) ((unsigned char) c)));
}

The product reads data past the end, or before the beginning, of the intended buffer.