CVE-2023-53566

A flaw was found in the Netfilter subsystem in the Linux kernel. A NULL pointer dereference and a use-after-free issue can be triggered due to an improper check and an improper way of iterating a red-black tree during garbage collector operations, potentially resulting in a denial of service and possibly privilege escalation.

The Netfilter subsystem as shipped in Red Hat Enterprise Linux 6, 7, 8 and 10 is not affected by this vulnerability because the vulnerable code is not present or is already fixed.

This issue has been fixed in Red Hat Enterprise Linux 9.0 and 9.3 via RHSA-2024:3421 [1] and RHSA-2023:6583 [2], respectively.

[1]. https://access.redhat.com/errata/RHSA-2024:3421

[2]. https://access.redhat.com/errata/RHSA-2023:6583

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.

1. This flaw can be mitigated by preventing the affected netfilter (nf_tables) kernel module from being loaded. For instructions on how to blacklist a kernel module, please see https://access.redhat.com/solutions/41278.

2. If the module cannot be disabled, on non-containerized deployments of Red Hat Enterprise Linux, the mitigation is to disable user namespaces:

# 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 the second mitigation (disabling user namespaces) as the functionality is needed to be enabled. The first mitigation (blacklisting nf_tables) is still viable for containerized deployments, providing the environment is not using netfilter.