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

Severity
Group ID
Group Title
Version
Rule ID
Date
STIG Version
mediumV-235021SRG-OS-000480-GPOS-00227SLES-15-040350SV-235021r991589_rule2025-02-272
Description
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.
ℹ️ Check
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
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