net/netfilter/nfnetlink_cthelper.c in the Linux kernel through 4.14.4 does
not require the CAP_NET_ADMIN capability for new, get, and del operations,
which allows local users to bypass intended access restrictions because the
nfnl_cthelper_list data structure is shared across all net namespaces.

It was discovered that the netfilter component of the Linux did not
properly restrict access to the connection tracking helpers list. A local
attacker could use this to bypass intended access restrictions.