This patch does not apply to 8.1RC-2, or 7.3-RELEASE
just accept whatever the project has corrected it to.

*** 8.0-RELEASE/src/libexec/rtld-elf/rtld.c	Sun Oct 25 02:10:29 2009
--- new-generic-from-sec-officer/src/libexec/rtld-elf/rtld.c	Tue Dec  1 17:31:53 2009
***************
*** 372,377 ****
--- 372,384 ----
          unsetenv(LD_ "LIBMAP_DISABLE");
          unsetenv(LD_ "DEBUG");
          unsetenv(LD_ "ELF_HINTS_PATH");
+ 		// http://people.freebsd.org/~cperciva/rtld.patch
+ 		if (unsetenv(LD_ "PRELOAD") || unsetenv(LD_ "LIBMAP") ||
+ 	    unsetenv(LD_ "LIBRARY_PATH") || unsetenv(LD_ "LIBMAP_DISABLE") ||
+ 	    unsetenv(LD_ "DEBUG") || unsetenv(LD_ "ELF_HINTS_PATH")) {
+ 		_rtld_error("environment corrupt; aborting");
+ 		die();
+ 	}
      }
      ld_debug = getenv(LD_ "DEBUG");
      libmap_disable = getenv(LD_ "LIBMAP_DISABLE") != NULL;
-------------------
http://xorl.wordpress.com/2009/12/01/freebsd-ld_preload-security-bypass/
-------------------
/pri/freebsd/releases grep -l unsetenv [4-8]*/src/libexec
6.3-RELEASE/src/libexec/rtld-elf/rtld.c
6.4-RELEASE/src/libexec/rtld-elf/rtld.c
7.1-RELEASE/src/libexec/rtld-elf/rtld.c
7.2-RELEASE/src/libexec/rtld-elf/rtld.c
8.0-RELEASE/src/libexec/rtld-elf/rtld.c