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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.
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.
________________________________________________________________________
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If you want to upgrade manually, download the updated package from one
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