Apply by doing:
	/usr/src
	patch -p0 < 013_pf.patch

Then build and install a new kernel.

Index: sys/net/pf.c
===================================================================
RCS file: /cvs/src/sys/net/pf.c,v
retrieving revision 1.690
retrieving revision 1.690.2.1
diff -u -p -r1.690 -r1.690.2.1
--- sys/net/pf.c	4 Feb 2010 14:10:12 -0000	1.690
+++ sys/net/pf.c	16 Feb 2011 19:13:44 -0000	1.690.2.1
@@ -1,4 +1,4 @@
-/*	$OpenBSD: pf.c,v 1.690 2010/02/04 14:10:12 sthen Exp $ */
+/*	$OpenBSD: pf.c,v 1.690.2.1 2011/02/16 19:13:44 sthen Exp $ */
 
 /*
  * Copyright (c) 2001 Daniel Hartmeier
@@ -2181,8 +2181,8 @@ pf_match_addr_range(struct pf_addr *b, s
 	switch (af) {
 #ifdef INET
 	case AF_INET:
-		if ((a->addr32[0] < b->addr32[0]) ||
-		    (a->addr32[0] > e->addr32[0]))
+		if ((ntohl(a->addr32[0]) < ntohl(b->addr32[0])) ||
+		    (ntohl(a->addr32[0]) > ntohl(e->addr32[0])))
 			return (0);
 		break;
 #endif /* INET */
@@ -2192,15 +2192,15 @@ pf_match_addr_range(struct pf_addr *b, s
 
 		/* check a >= b */
 		for (i = 0; i < 4; ++i)
-			if (a->addr32[i] > b->addr32[i])
+			if (ntohl(a->addr32[i]) > ntohl(b->addr32[i]))
 				break;
-			else if (a->addr32[i] < b->addr32[i])
+			else if (ntohl(a->addr32[i]) < ntohl(b->addr32[i]))
 				return (0);
 		/* check a <= e */
 		for (i = 0; i < 4; ++i)
-			if (a->addr32[i] < e->addr32[i])
+			if (ntohl(a->addr32[i]) < ntohl(e->addr32[i]))
 				break;
-			else if (a->addr32[i] > e->addr32[i])
+			else if (ntohl(a->addr32[i]) > ntohl(e->addr32[i]))
 				return (0);
 		break;
 	}