Apply by doing:
	cd /usr/src
	patch -p0 < 020_sudo.patch

And then rebuild and install sudo:
	cd usr.bin/sudo
	make -f Makefile.bsd-wrapper obj
	make -f Makefile.bsd-wrapper cleandir
	make -f Makefile.bsd-wrapper
	make -f Makefile.bsd-wrapper install

Index: usr.bin/sudo/check.c
===================================================================
RCS file: /cvs/src/usr.bin/sudo/check.c,v
retrieving revision 1.5.4.1
diff -u -r1.5.4.1 check.c
--- usr.bin/sudo/check.c	18 Jan 2002 16:14:44 -0000	1.5.4.1
+++ usr.bin/sudo/check.c	25 Apr 2002 15:50:09 -0000
@@ -196,9 +196,9 @@
 
     if (subst) {
 	new_prompt = (char *) emalloc(len + 1);
-	for (p = old_prompt, np = new_prompt; *p; p++) {
+	for (p = old_prompt, np = new_prompt, lastchar = '\0'; *p; p++) {
 	    if (lastchar == '%' && (*p == 'h' || *p == 'u' || *p == '%')) {
-		/* substiture user/host name */
+		/* substitute user/host name */
 		if (*p == 'h') {
 		    np--;
 		    strcpy(np, user_shost);