--- ucd-snmp-4.2.5/snmplib/snmp_api.c.DoS	2005-08-03 17:16:17.000000000 +0200
+++ ucd-snmp-4.2.5/snmplib/snmp_api.c	2005-08-03 17:22:12.000000000 +0200
@@ -4120,7 +4120,7 @@
         else
           isp->proper_len = asn_check_packet(isp->packet, isp->packet_len);
 
-        if (isp->proper_len > MAX_PACKET_LENGTH) {
+        if (isp->proper_len > MAX_PACKET_LENGTH || isp->proper_len < 0) {
           /* illegal length, drop the connection */
           snmp_log(LOG_ERR,"Maximum packet size exceeded in a request.\n");
           isp->sd = -1;