CVE-2020-36694

A use-after-free flaw was found in the packet processing context in net/netfilter/x_tables.c in netfilter in the Linux Kernel. This issue occurs when the per-CPU sequence count is mishandled during concurrent iptables rules replacement and can be exploited with the CAP_NET_ADMIN capability in an unprivileged namespace.

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.

In order to trigger the issue, it requires the ability to create user/net namespaces.

On non-containerized deployments of Red Hat Enterprise Linux 8, 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.