The SUSE operating system must not allow interfaces to accept Internet Protocol version 6 (IPv6) Internet Control Message Protocol (ICMP) redirect messages by default.

From SLES 12 Security Technical Implementation Guide

Associated with: CCI-000366

SV-96519r1_rule The SUSE operating system must not allow interfaces to accept Internet Protocol version 6 (IPv6) Internet Control Message Protocol (ICMP) redirect messages by default.

Vulnerability 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 allow IPv6 ICMP redirect messages by default. Check the value of the "default accept_redirects" variables with the following command: # sudo sysctl net.ipv6.conf.default.accept_redirects net.ipv6.conf.default.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 not allow IPv6 ICMP redirect messages by default. Set the 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.ipv6.conf.default.accept_redirects=0 Run the following command to apply this value: # sysctl –system

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