Title

The Ubuntu operating system must not send Internet Protocol version 4 (IPv4) Internet Control Message Protocol (ICMP) redirects. (Cat II impact)

Discussion

Internet Control Message Protocol (ICMP) redirect messages are used by routers to inform hosts that a more direct route exists for a particular destination. These messages contain information from the system's route table, possibly revealing portions of the network topology.

Check Content

Verify the Ubuntu operating system does not send Internet Protocol version 4 (IPv4) Internet Control Message Protocol (ICMP) redirect messages. Check the value of the "all send_redirects" variables with the following command: # sudo sysctl net.ipv4.conf.all.send_redirects net.ipv4.conf.all.send_redirects=0 If the returned line does not have a value of "0", or a line is not returned, this is a finding.

Fix Text

Configure the Ubuntu operating system to not allow interfaces to perform Internet Protocol version 4 (IPv4) Internet Control Message Protocol (ICMP) redirects with the following command: # sudo sysctl -w net.ipv4.conf.all.send_redirects=0 If "0" is not the system's default value then add or update the following line in "/etc/sysctl.conf" or in the appropriate file under "/etc/sysctl.d": net.ipv4.conf.all.send_redirects=0

Additional Identifiers

Rule ID: SV-90565r2_rule

Vulnerability ID: V-75885

Group Title:

Expert Comments

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