CVE-2024-1086

A flaw was found in the Netfilter subsystem in the Linux kernel. This issue occurs in the nft_verdict_init() function, allowing positive values as a drop error within the hook verdict, therefore, the nf_hook_slow() function can cause a double-free vulnerability when NF_DROP is issued with a drop error that resembles NF_ACCEPT. The nf_tables component can be exploited to achieve local privilege escalation.

This flaw is rated as having an Important impact. There is the limitation that it can only be exploited by a local user with access to Netfilter, but can still allow privilege escalation if user namespaces are enabled and Netfilter is being used.

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.