RHEL 9 must limit the number of bogus Internet Control Message Protocol (ICMP) response errors logs.

Severity	Group ID	Group Title	Version	Rule ID	Date	STIG Version
medium	V-257967	SRG-OS-000480-GPOS-00227	RHEL-09-253060	SV-257967r1155745_rule	2025-11-24	2

Description
Some routers will send responses to broadcast frames that violate RFC-1122, which fills up a log file system with many useless error messages. An attacker may take advantage of this and attempt to flood the logs with bogus error logs. Ignoring bogus ICMP error responses reduces log size, although some activity would not be logged. The sysctl --system command will load settings from all system configuration files. All configuration files are sorted by their filename in lexicographical order, regardless of the directories in which they reside. If multiple files specify the same option, the entry in the file with the lexicographically latest name will take precedence. Files are read from directories in the following list from top to bottom. Once a file of a given filename is loaded, any file of the same name in subsequent directories is ignored. /etc/sysctl.d/.conf /run/sysctl.d/.conf /usr/local/lib/sysctl.d/.conf /usr/lib/sysctl.d/.conf /lib/sysctl.d/*.conf /etc/sysctl.conf

Description

Some routers will send responses to broadcast frames that violate RFC-1122, which fills up a log file system with many useless error messages. An attacker may take advantage of this and attempt to flood the logs with bogus error logs. Ignoring bogus ICMP error responses reduces log size, although some activity would not be logged. The sysctl --system command will load settings from all system configuration files. All configuration files are sorted by their filename in lexicographical order, regardless of the directories in which they reside. If multiple files specify the same option, the entry in the file with the lexicographically latest name will take precedence. Files are read from directories in the following list from top to bottom. Once a file of a given filename is loaded, any file of the same name in subsequent directories is ignored. /etc/sysctl.d/*.conf /run/sysctl.d/*.conf /usr/local/lib/sysctl.d/*.conf /usr/lib/sysctl.d/*.conf /lib/sysctl.d/*.conf /etc/sysctl.conf

ℹ️ Check
Verify RHEL 9 limits the number of bogus Internet Control Message Protocol (ICMP) response errors logs. Check the value of the "net.ipv4.icmp_ignore_bogus_error_response" variables with the following command: $ sudo sysctl net.ipv4.icmp_ignore_bogus_error_responses net.ipv4.icmp_ignore_bogus_error_responses = 1 If "net.ipv4.icmp_ignore_bogus_error_response" is not set to "1" or is missing, this is a finding.

ℹ️ Check

Verify RHEL 9 limits the number of bogus Internet Control Message Protocol (ICMP) response errors logs. Check the value of the "net.ipv4.icmp_ignore_bogus_error_response" variables with the following command: $ sudo sysctl net.ipv4.icmp_ignore_bogus_error_responses net.ipv4.icmp_ignore_bogus_error_responses = 1 If "net.ipv4.icmp_ignore_bogus_error_response" is not set to "1" or is missing, this is a finding.

✔️ Fix
Configure RHEL 9 to not log bogus ICMP errors: Create a configuration file if it does not already exist: $ sudo vi /etc/sysctl.d/ipv4_icmp_ignore_bogus_error_responses.conf Add the following line to the file: net.ipv4.icmp_ignore_bogus_error_responses = 1 Reload settings from all system configuration files with the following command: $ sudo sysctl --system