Vulnerability Discussion

Responding to broadcast (ICMP) echoes facilitates network mapping and provides a vector for amplification attacks.

Ignoring ICMP echo requests (pings) sent to broadcast or multicast addresses makes the system slightly more difficult to enumerate on the network.

Satisfies: SRG-OS-000420-GPOS-00186, SRG-OS-000142-GPOS-00080

Check

Verify RHEL 10 ignores ICMP echoes sent to a broadcast address.

Check the value of the "net.ipv4.icmp_echo_ignore_broadcasts" variable with the following command:

$ sudo sysctl net.ipv4.icmp_echo_ignore_broadcasts
net.ipv4.icmp_echo_ignore_broadcasts = 1

If "net.ipv4.icmp_echo_ignore_broadcasts" is not set to "1" or is missing, this is a finding.

Fix

Configure RHEL 10 to ignore Internet Protocol version 4 (IPv4) ICMP echoes sent to a broadcast address.

Create a configuration file if it does not already exist:

$ sudo vi /etc/sysctl.d/ipv4_icmp_echo_ignore_broadcasts.conf

Add the following line to the file:

net.ipv4.icmp_echo_ignore_broadcasts = 1

Reload settings from all system configuration files with the following command:

$ sudo sysctl --system