Rule version RHEL-10-800090 · STIG v1 · 2026-09-17
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.
This feature of the IPv4 protocol has few legitimate uses. It should be disabled unless absolutely required.
Satisfies: SRG-OS-000420-GPOS-00186, SRG-OS-000142-GPOS-00072
Verify RHEL 10 will not accept IPv4 ICMP redirect messages.
Check the value of all "net.ipv4.conf.all.accept_redirects" variables with the following command:
$ sudo sysctl net.ipv4.conf.all.accept_redirects net.ipv4.conf.all.accept_redirects = 0
If "net.ipv4.conf.all.accept_redirects" is not set to "0" or is missing, this is a finding.
Configure RHEL 10 to ignore IPv4 ICMP redirect messages.
Create a configuration file if it does not already exist:
$ sudo vi /etc/sysctl.d/99-ipv4_accept_redirects.conf
Add the following line to the file:
net.ipv4.conf.all.accept_redirects = 0
Reload settings from all system configuration files with the following command:
$ sudo sysctl --system