Title

RHEL 9 must disable access to network bpf system call from nonprivileged processes. (Cat II impact)

Discussion

Loading and accessing the packet filters programs and maps using the bpf() system call has the potential of revealing sensitive information about the kernel state. Satisfies: SRG-OS-000132-GPOS-00067, SRG-OS-000480-GPOS-00227

Check Content

Verify that RHEL 9 prevents privilege escalation through the kernel by disabling access to the bpf system call with the following commands: $ sysctl kernel.unprivileged_bpf_disabled kernel.unprivileged_bpf_disabled = 1 If the returned line does not have a value of "1", or a line is not returned, this is a finding. Check that the configuration files are present to enable this kernel parameter. $ sudo /usr/lib/systemd/systemd-sysctl --cat-config | egrep -v '^(#|;)' | grep -F kernel.unprivileged_bpf_disabled | tail -1 kernel.unprivileged_bpf_disabled = 1 If the network parameter "kernel.unprivileged_bpf_disabled" is not equal to "1", or nothing is returned, this is a finding.

Fix Text

Configure the currently loaded kernel parameter to the secure setting: $ sudo sysctl -w kernel.unprivileged_bpf_disabled=1 Configure RHEL 9 to prevent privilege escalation through the kernel by disabling access to the bpf syscall by adding the following line to a file in the "/etc/sysctl.d" directory: kernel.unprivileged_bpf_disabled = 1 The system configuration files must be reloaded for the changes to take effect. To reload the contents of the files, run the following command: $ sysctl --system

Additional Identifiers

Rule ID: SV-257810r1044869_rule

Vulnerability ID: V-257810

Group Title: SRG-OS-000132-GPOS-00067

Expert Comments

CCIs tied to check.

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