http://www.freebsd.org/security/advisories/FreeBSD-SA-13:08.nfsserver.asc
https://bugs.gentoo.org/show_bug.cgi?id=478314

Index: sys/kern/vfs_export.c
===================================================================
--- sys/kern/vfs_export.c	(revision 253367)
+++ sys/kern/vfs_export.c	(working copy)
@@ -208,7 +208,7 @@
 	np->netc_anon = crget();
 	np->netc_anon->cr_uid = argp->ex_anon.cr_uid;
 	crsetgroups(np->netc_anon, argp->ex_anon.cr_ngroups,
-	    np->netc_anon->cr_groups);
+	    argp->ex_anon.cr_groups);
 	np->netc_anon->cr_prison = &prison0;
 	prison_hold(np->netc_anon->cr_prison);
 	np->netc_numsecflavors = argp->ex_numsecflavors;