CVE-2026-78408 Util-linux: util-linux: nsenter --join-cgroup leaks root cgroup migration authority
An attacker can exploit nsenter to inherit root cgroup migration authority, allowing them to move or terminate unrelated root processes.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- A user has to click or open something
- Fix
- Available
What is CVE-2026-78408?
CVE-2026-78408 is a high-severity vulnerability in Red Hat Enterprise Linux 10, published on 2 Sep 2026. It can only be exploited from the same machine or local network, and only if a user opens a file or follows a link.
Official description
The nsenter --join-cgroup option opens the target cgroup.procs file as root and leaves that file descriptor open across later namespace and credential changes and across execve(). Because the kernel checks later cgroup migrations using the credentials from the original open, a program run in an attacker-controlled target can inherit root's ability to move host processes between cgroups. After a privileged operator uses --join-cgroup against that target, an unprivileged user can migrate and terminate unrelated root processes.
Weakness: CWE-775
Which versions are affected by CVE-2026-78408?
How do I fix CVE-2026-78408?
Apply the vendor's patch.
Is CVE-2026-78408 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-78408 exists.
Sources
Also known as ALPINE-CVE-2026-78408, AZL-99393, BELL-CVE-2026-78408, DEBIAN-CVE-2026-78408, ECHO-3f6d-9602-8caa, ROOT-OS-DEBIAN-12-CVE-2026-78408 and 2 more.