https://bugs.gentoo.org/600174
https://lists.gnu.org/archive/html/bug-bash/2016-11/msg00099.html

*** bash-4.4/builtins/pushd.def
--- bash-4.4/builtins/pushd.def
***************
*** 366,370 ****
      }
  
!   if (which > directory_list_offset || (directory_list_offset == 0 && which == 0))
      {
        pushd_error (directory_list_offset, which_word ? which_word : "");
--- 366,370 ----
      }
  
!   if (which > directory_list_offset || (which < -directory_list_offset) || (directory_list_offset == 0 && which == 0))
      {
        pushd_error (directory_list_offset, which_word ? which_word : "");
***************
*** 388,391 ****
--- 388,396 ----
  	 of the list into place. */
        i = (direction == '+') ? directory_list_offset - which : which;
+       if (i < 0 || i > directory_list_offset)
+ 	{
+ 	  pushd_error (directory_list_offset, which_word ? which_word : "");
+ 	  return (EXECUTION_FAILURE);
+ 	}
        free (pushd_directory_list[i]);
        directory_list_offset--;