The Red Hat Security Advisory warns Netfilter ("iptables") can leak information about how port forwarding is done in unfiltered ICMP packets.
This bug only affects users using the Network Address Translation features of firewalls built with netfilter ("iptables"). Red Hat Linux's firewall configuration tools use "ipchains," and those configurations are not vulnerable to this bug. The older "ipchains" code is not affected.
For more information on a work-around check out: http://bugzilla.redhat.com/bugzilla