SLEM 5 must not allow interfaces to accept Internet Protocol version 4 (IPv4) Internet Control Message Protocol (ICMP) redirect messages by default.
Overview
| Finding ID | Version | Rule ID | IA Controls | Severity |
| V-261316 | SLEM-05-253025 | SV-261316r996418_rule | CCI-000366 | 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 | 2025-05-08 | |||
Details
Check Text (C-261316r996418_chk)
Verify SLEM 5 does not accept IPv4 ICMP redirect messages by default with the following command:
> sudo sysctl net.ipv4.conf.default.accept_redirects
net.ipv4.conf.default.accept_redirects = 0
If the network parameter "ipv4.conf.default.accept_redirects" is not equal to "0", or nothing is returned, this is a finding.
Fix Text (F-64953r996417_fix)
Configure SLEM 5 to not accept IPv4 ICMP redirect messages by default by running the following command as an administrator:
> sudo sysctl -w net.ipv4.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.ipv4.conf.default.accept_redirects=0" >> /etc/sysctl.d/99-stig.conf'
> sudo sysctl --system