A flaw was found in the Linux kernel in net/netfilter/nf_tables_core.c:nft_do_chain, which can cause a use-after-free. This issue needs to handle ‘return’ with proper preconditions, as it can lead to a kernel information leak problem caused by a local, unprivileged attacker.

Mitigation

On non-containerized deployments of Red Hat Enterprise Linux, you can disable user namespaces by setting user.max_user_namespaces to 0:

echo "user.max_user_namespaces=0" > /etc/sysctl.d/userns.conf

sysctl -p /etc/sysctl.d/userns.conf

On containerized deployments, such as Red Hat OpenShift Container Platform, do not use this mitigation as the functionality is needed to be enabled.