Title

SLEM 5 must not allow interfaces to accept Internet Protocol version 6 (IPv6) Internet Control Message Protocol (ICMP) redirect messages by default. (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 SLEM 5 does not allow IPv6 ICMP redirect messages by default with the following command: > sudo sysctl net.ipv6.conf.default.accept_redirects net.ipv6.conf.default.accept_redirects = 0 If the network parameter "ipv6.conf.default.accept_redirects" is not equal to "0", or nothing is returned, this is a finding.

Fix Text

Configure SLEM 5 to not accept IPv6 ICMP redirect messages by default by running the following command as an administrator: > sudo sysctl -w net.ipv6.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.ipv6.conf.default.accept_redirects=0" >> /etc/sysctl.d/99-stig.conf' > sudo sysctl --system

Additional Identifiers

Rule ID: SV-261324r996442_rule

Vulnerability ID: V-261324

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

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