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The Ubuntu operating system must not forward Internet Protocol version 4 (IPv4) source-routed packets.


Overview

Finding ID Version Rule ID IA Controls Severity
V-215146 UBTU-16-030530 SV-215146r508033_rule Medium
Description
Source-routed packets allow the source of the packet to suggest that routers forward the packet along a different path than configured on the router, which can be used to bypass network security measures. This requirement applies only to the forwarding of source-routed traffic, such as when IPv4 forwarding is enabled and the system is functioning as a router.
STIG Date
Canonical Ubuntu 16.04 LTS Security Technical Implementation Guide 2020-09-03

Details

Check Text ( C-16345r285306_chk )
Verify the Ubuntu operating system does not accept IPv4 source-routed packets.

Check the value of the accept source route variable with the following command:

# sudo sysctl net.ipv4.conf.all.accept_source_route

net.ipv4.conf.all.accept_source_route=0

If the returned line does not have a value of "0", a line is not returned, or the returned line is commented out, this is a finding.
Fix Text (F-16343r285307_fix)
Configure the Ubuntu operating system to not forward Internet Protocol version 4 (IPv4) source-routed packets with the following command:

# sudo sysctl -w net.ipv4.conf.all.accept_source_route=0

If "0" is not the system's default value then add or update the following line in "/etc/sysctl.conf" or in the appropriate file under "/etc/sysctl.d":

net.ipv4.conf.all.accept_source_route=0