append_utf8_value (const unsigned char *value, size_t length,
                   struct stringbuf *sb)
{
  unsigned char tmp[6];
  const unsigned char *s;
  size_t n;
  int i, nmore;

  if (length && (*value == ' ' || *value == '#'))
    {
      tmp[0] = '\\';
      tmp[1] = *value;
      put_stringbuf_mem (sb, tmp, 2);
      value++;
      length--;
    }
  if (length && value[length-1] == ' ')
    {
      tmp[0] = '\\';
      tmp[1] = ' ';
      put_stringbuf_mem (sb, tmp, 2);
       length--;
     }
 
   for (s=value, n=0;;)
     {
       for (value = s; n < length && !(*s & 0x80); n++, s++)
      for (value = s; n < length && !(*s & 0x80); n++, s++)
        ;
         append_quoted (sb, value, s-value, 0);
       if (n==length)
         return; /* ready */
      if (!(*s & 0x80))
        nmore = 0; /* Not expected here: high bit not set.  */
      else if ( (*s & 0xe0) == 0xc0 ) /* 110x xxxx */
         nmore = 1;
       else if ( (*s & 0xf0) == 0xe0 ) /* 1110 xxxx */
         nmore = 2;
      else if ( (*s & 0xf8) == 0xf0 ) /* 1111 0xxx */
        nmore = 3;
      else if ( (*s & 0xfc) == 0xf8 ) /* 1111 10xx */
         nmore = 4;
       else if ( (*s & 0xfe) == 0xfc ) /* 1111 110x */
         nmore = 5;
      else /* Invalid encoding */
        nmore = 0;
 
      if (!nmore)
         {
          /* Encoding error:  We quote the bad byte.  */
          snprintf (tmp, sizeof tmp, "\\%02X", *s);
          put_stringbuf_mem (sb, tmp, 3);
          s++; n++;
        }
      else
        {
          if (n+nmore > length)
            nmore = length - n; /* Oops, encoding to short */

          tmp[0] = *s++; n++;
          for (i=1; i <= nmore; i++)
            {
              if ( (*s & 0xc0) != 0x80)
                break; /* Invalid encoding - let the next cycle detect this. */
              tmp[i] = *s++;
              n++;
            }
          put_stringbuf_mem (sb, tmp, i);
         }
     }
 }

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.