SLEM 5 must not allow interfaces to accept Internet Protocol version 4 (IPv4) Internet Control Message Protocol (ICMP) redirect messages by default.
Severity | Group ID | Group Title | Version | Rule ID | Date | STIG Version |
|---|---|---|---|---|---|---|
| medium | V-261316 | SRG-OS-000480-GPOS-00227 | SLEM-05-253025 | SV-261316r996418_rule | 2024-06-04 | 1 |
| 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 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 |
|---|
| 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 |