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The SUSE operating system must not allow interfaces to accept Internet Protocol version 6 (IPv6) Internet Control Message Protocol (ICMP) redirect messages by default.


Finding ID Version Rule ID IA Controls Severity
V-235021 SLES-15-040350 SV-235021r622137_rule Medium
ICMP redirect messages are used by routers to inform hosts that a more direct route exists for a particular destination. These messages modify the host's route table and are unauthenticated. An illicit ICMP redirect message could result in a man-in-the-middle attack.
SUSE Linux Enterprise Server 15 Security Technical Implementation Guide 2022-12-07


Check Text ( C-38209r619332_chk )
Verify the SUSE operating system does not allow IPv6 ICMP redirect messages by default.

Check the value of the default IPv6 accept_redirects variable with the following command:

> sudo sysctl net.ipv6.conf.default.accept_redirects
net.ipv6.conf.default.accept_redirects = 0

If the network parameter "ipv6.conf.default.accept_redirects" is not equal to "0" or nothing is returned, this is a finding.
Fix Text (F-38172r619333_fix)
Configure the SUSE operating system to not accept IPv6 ICMP redirect messages by default by running the following command as an administrator:

> sudo sysctl -w net.ipv6.conf.default.accept_redirects=0

If "0" is not the system's default value, add or update the following line in "/etc/sysctl.d/99-stig.conf":

> sudo sh -c 'echo "net.ipv6.conf.default.accept_redirects=0" >> /etc/sysctl.d/99-stig.conf'

> sudo sysctl --system