Bug 192888 - ipfw NAT vulnerable to simple DOS attacks
Summary: ipfw NAT vulnerable to simple DOS attacks
Status: New
Alias: None
Product: Base System
Classification: Unclassified
Component: kern (show other bugs)
Version: 9.2-RELEASE
Hardware: Any Any
: --- Affects Many People
Assignee: freebsd-ipfw (Nobody)
Depends on:
Reported: 2014-08-21 13:57 UTC by napTu
Modified: 2020-09-20 11:26 UTC (History)
2 users (show)

See Also:


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Description napTu 2014-08-21 13:57:22 UTC
ipfw NAT vulnerable to DOS attacks by sending ip packets to external ip address and any port.
In this situation CPU usage goes to 100%.

NAT should find a matched internal address, and, if not, skip the packet to external ip.

This process (with failed search) take a many time and resources.
Comment 1 Tom Jones freebsd_committer 2020-09-19 16:35:58 UTC
Could you add some more detail or steps to reproduce? If this issue still exists in FreeBSD I would be very interested in fixing this. If I don't have any response in the next few months I will close this issue.
Comment 2 lutz 2020-09-20 11:26:08 UTC
It seems that the problems still exists:
(Articles in German)

It's a variant of the LAND attack https://en.wikipedia.org/wiki/LAND.

My solution is to use ipfw (which is used to activate NAT) to drop incoming packets sourced from the public NAT IP. So simple antispoofing.