- Package name
- Advisory ID
- Affected versions
- 8.1 i586 , 8.0 i586 , 8.2 i586
A problem was discovered with Netfilter Network Address Translation (NAT) capabilities. It was found that iptables can leak information about how port forwarding is accomplished in unfiltered ICMP packets. When a NAT rule applies to the first packet of a connection, which subsequently causes the system to generate an ICMP error message, the ICMP error message is transmitted including the translated address. This information gives the IP address of the system to which the connection would have been forwarded had the error message not been generated, exposing information about the netfilter configuration and the network topology. There is currently no clean fix for this problem, but a fix is being worked on. In the meantime, if you use the NAT capabilities of iptables, you can protect yourself by filtering out untracked local ICMP packets using the following iptables command: iptables -A OUTPUT -m state -p icmp --state INVALID -j DROP All kernel patches from iptables < 1.2.6a are vulnerable. All kernel versions from 2.4.4 and up to (at least) 2.4.19-pre6 use a vulnerable version. Thanks to Philippe Biondi for discovering this problem.