Title

The SUSE operating system must prevent Internet Protocol version 4 (IPv4) Internet Control Message Protocol (ICMP) redirect messages from being accepted. (Cat II impact)

Discussion

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.

Check Content

Verify the SUSE operating system does not accept ICMP redirect messages. Check the value of the "net.ipv4.conf.all.accept_redirects" variable with the following command: # sysctl net.ipv4.conf.all.accept_redirects net.ipv4.conf.all.accept_redirects =0 If the returned line does not have a value of "0" this is a finding.

Fix Text

Configure the SUSE operating system to the required kernel parameter by adding the following line to "/etc/sysctl.conf" (or modify the line to have the required value): net.ipv4.conf.all.accept_redirects =0 Run the following command to apply this value: # sysctl --system

Additional Identifiers

Rule ID: SV-217291r603262_rule

Vulnerability ID: V-217291

Group Title: SRG-OS-000480-GPOS-00227

Expert Comments

CCIs tied to check.

Controls tied to check. These are derived from the CCIs shown above.