CVE-2026-23111

A flaw was found in the Linux kernel's nf_tables component. A logic bug in nft_map_catchall_activate causes an inverted element activity check during the abort path of a failed transaction. This can lead to a use-after-free vulnerability, as catchall verdict elements may still reference a freed chain. A local low privileged user can exploit this to cause a denial of service or potentially achieve privilege escalation.

A logic bug in nf_tables nft_map_catchall_activate uses an inverted element active check during the abort path of a failed transaction. This can prevent re activation of catchall map elements and for NFT_GOTO verdict elements it can skip restoring the chain use reference count. Repeating an abort sequence can permanently decrement chain use until DELCHAIN frees the chain while catchall elements still reference it which can result in a use after free. For the CVSS the PR is L, but in the paranoid scenario the unprivileged users may reach nf_tables via user namespaces with delegated CAP_NET_ADMIN. The issue is not directly network reachable and is triggered by local nftables control plane operations. Impact can range from denial of service to potential privilege escalation depending on heap reuse.

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.

To mitigate this issue, prevent module nf_tables from being loaded. Please see https://access.redhat.com/solutions/41278 for how to blacklist a kernel module to prevent it from loading automatically.