Already fixed upstream, should appear in 5.4.1
--- net-snmp-5.4/agent/mibgroup/udp-mib/data_access/udp_endpoint_linux.c.orig	2006-09-19 05:26:57.000000000 +0200
+++ net-snmp-5.4/agent/mibgroup/udp-mib/data_access/udp_endpoint_linux.c	2007-05-03 13:21:55.000000000 +0200
@@ -194,7 +194,7 @@
                     offset, line_info->start));
         return PMLP_RC_MEMORY_UNUSED;
     }
-    ep->loc_addr_len = offset;
+    ep->rmt_addr_len = offset;
     ptr += (offset * 2);
     ++ptr; /* skip ':' */