Util linux: The nsenter --join-cgroup option opens the target cgroup.procs file as root and leaves that file
Affects util-linuxSource GCVE Database
Not known to be exploited · CVSS 7.9 High · fixed in 2.41.6 : patch util-linux soon.
Data as of 9 Nov 2026, 13:55 UTC
Thin evidence
One scorer or none| CNA (redhat) | CVSS 3.1 | 7.9 |
|---|
- Patch
- Available – fixed in 2.41.6
CVSS:3.1/AV:L/AC:L/PR:L/UI:R/S:C/C:N/I:H/A:HExploitation evidence
Disclosed: evidence found.
CVE published 2 Sep 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors
A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 9 Nov 2026.
What to do
Affected software
| Product | Affected | Fixed in |
|---|---|---|
Ubuntu 26.10util-linuxpkg:deb/ubuntu/util-linux?arch=source&distro=stonkingOther threats | Affected
| Fixed in– |
Ubuntu 26.04 LTSutil-linuxpkg:deb/ubuntu/util-linux?arch=source&distro=resoluteOther threats | Affected
| Fixed in– |
Ubuntu Pro 20.04 LTSutil-linuxpkg:deb/ubuntu/util-linux?arch=source&distro=esm-infra/focalOther threats | Affected
| Fixed in– |
Ubuntu 18.04 LTSutil-linuxpkg:deb/ubuntu/util-linux?arch=source&distro=bionicOther threats | Affected
| Fixed in– |
Ubuntu Pro 16.04 LTSutil-linuxpkg:deb/ubuntu/util-linux?arch=source&distro=esm-infra/xenialOther threats | Affected
| Fixed in– |
Ubuntu 14.04 LTSutil-linuxpkg:deb/ubuntu/util-linux?arch=source&distro=trustyOther threats | Affected
| Fixed in– |
Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.
AI-suggested
Upgrade util-linux to version 2.41.6, 2.42.3, or later. If you cannot patch yet, avoid running nsenter --join-cgroup (including nsenter --target PID --all --join-cgroup) against untrusted processes or namespaces.
Description
A vulnerability in util-linux's nsenter tool (introduced in v2.40) allows a privileged operator using the --join-cgroup option to open the target cgroup.procs file as root and leave the file descriptor open across namespace and credential changes. This behavior enables an unprivileged user in an attacker-controlled target to inherit root's ability to migrate and terminate unrelated root processes. The issue is fixed in util-linux versions 2.41.6 and 2.42.3.
References
- ubuntu.com/security/CVE-2026-78408 (opens in a new tab)
- cve.org/CVERecord?id=CVE-2026-78408 (opens in a new tab)
- github.com/util-linux/util-linux/security/advisories/GHSA-55fx-f4gg-cfhj (opens in a new tab)
- access.redhat.com/security/cve/CVE-2026-78408 (opens in a new tab)
- bugzilla.redhat.com/show_bug.cgi?id=2522497 (opens in a new tab)