Linux Kernel Bug Caused by Single Character Opens Path to Root Access

CVE-2026-23111 is a high-severity use-after-free vulnerability in the Linux nf_tables firewall framework caused by a misplaced negation operator; it allows unprivileged local users (and in some cases containerized workloads) to escalate to root. The bug was fixed with a one-character change upstream in Feb 2026 and patches have been distributed by major vendors, but public proof-of-concept and working exploit code were published thereafter, prompting urgent recommendations to apply kernel updates, reboot systems, and consider disabling unprivileged user namespaces where feasible.