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SLEM 5 must not allow interfaces to accept Internet Protocol version 6 (IPv6) Internet Control Message Protocol (ICMP) redirect messages by default.


Overview

Finding ID Version Rule ID IA Controls Severity
V-261324 SLEM-05-254025 SV-261324r996442_rule Medium
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.
STIG Date
SUSE Linux Enterprise Micro (SLEM) 5 Security Technical Implementation Guide 2024-06-04

Details

Check Text ( C-65053r996440_chk )
Verify SLEM 5 does not allow IPv6 ICMP redirect messages by default 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-64961r996441_fix)
Configure SLEM 5 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