CVE-2026-78408

Name	CVE-2026-78408
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.
Source	CVE (at NVD; CERT, ENISA, LWN, oss-sec, fulldisc, Debian ELTS, Red Hat, Ubuntu, Gentoo, SUSE bugzilla/CVE, GitHub advisories/code/issues, web search, more)

Vulnerable and fixed packages

The table below lists information on source packages.

Source Package	Release	Version	Status
util-linux (PTS)	bookworm	2.38.1-5+deb12u3	vulnerable
	bookworm (security)	2.38.1-5+deb12u1	vulnerable
	trixie (security), trixie	2.41.5-0+deb13u1	vulnerable
	forky	2.42.2-4	vulnerable
	sid	2.42.3-1	fixed

The information below is based on the following data on fixed versions.

Package	Type	Release	Fixed Version	Urgency	Origin	Debian Bugs
util-linux	source	(unstable)	2.42.3-1

[trixie] - util-linux <no-dsa> (Minor issue)
https://github.com/util-linux/util-linux/security/advisories/GHSA-55fx-f4gg-cfhj