A use-after-free vulnerability was found in the Linux kernel's Netfilter
subsystem in net/netfilter/nf_tables_api.c. This flaw allows a local
attacker with user access to cause a privilege escalation issue.

Aaron Adams discovered that the netfilter subsystem in the Linux kernel did
not properly handle the removal of stateful expressions in some situations,
leading to a use-after-free vulnerability. A local attacker could use this
to cause a denial of service (system crash) or execute arbitrary code.

If not needed, disable the ability for unprivileged users
to create namespaces:

$ sudo sysctl -w kernel.unprivileged_userns_clone=0
$ echo kernel.unprivileged_userns_clone=0 | \
    sudo tee /etc/sysctl.d/99-disable-unpriv-userns.conf