by George Whittaker Ubuntu administrators running containerized workloads have a new Linux kernel security problem to watch closely. Public exploit code is now available for CVE-2026-80521, a Linux kernel use-after-free vulnerability that can allow an unprivileged process inside a container to escape and obtain root privileges on the underlying host. Security firm DepthFirst published its research and exploit on September 22, 2026, demonstrating the attack against Ubuntu 26.04 LTS. The underlying Linux kernel vulnerability had already been fixed upstream on August 6, but as of September 23, Ubuntu's security tracker still lists the main kernel package in Ubuntu 26.04 LTS as "Vulnerable, work in progress," while Ubuntu 24.04 LTS is also listed as vulnerable. The situation is particularly important for Docker, Kubernetes, cloud infrastructure, and other environments that run potentially untrusted workloads because the vulnerable kernel functionality can be reached through ordinary operat