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

From SLES 12 Security Technical Implementation Guide

Associated with: CCI-000366

SV-92185r3_rule The SUSE operating system must not forward Internet Protocol version 4 (IPv4) source-routed packets by default.

Vulnerability discussion

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.

Check content

Verify the SUSE operating system does not accept IPv4 source-routed packets by default. Check the value of the default accept source route variable with the following command: # sysctl net.ipv4.conf.default.accept_source_route net.ipv4.conf.default.accept_source_route = 0 If the returned line does not have a value of "0" this is a finding.

Fix text

Configure the SUSE operating system to the required kernel parameter by adding the following line to "/etc/sysctl.conf" (or modify the line to have the required value): net.ipv4.conf.default.accept_source_route = 0 Run the following command to apply this value: # sysctl --system

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