Vulnerability 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.

Check

Verify AlmaLinux OS 9 prevents privilege escalation thru 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.

$ /usr/lib/systemd/systemd-sysctl --cat-config | egrep -v '^(#|;)' | grep -F kernel.unprivileged_bpf_disabled | tail -1

kernel.unprivileged_bpf_disabled = 1

If "kernel.unprivileged_bpf_disabled" is not set to "1", or nothing is returned, this is a finding.

Fix

Configure AlmaLinux OS 9 to prevent privilege escalation through the kernel by disabling access to the bpf syscall with the following command:

$ echo "kernel.unprivileged_bpf_disabled = 1" > /etc/sysctl.d/60-bpf.conf

Load settings from all system configuration files with the following command:

$ sysctl --system