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CVE-2026-78408VulnerabilityPublished Updated

Util linux: The nsenter --join-cgroup option opens the target cgroup.procs file as root and leaves that file

Affects util-linuxSource GCVE Database

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Authoritative record:CVE-2026-78408· High 7.9

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

CVSS 3.1 base score
7.9High
How severe the flaw is on the 0–10 CVSS scale.

Thin evidence

One scorer or none
CVSS scores by source
CNA (redhat)CVSS 3.17.9
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:H

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 2 Sep 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponized: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq 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

ProductAffectedFixed in
Ubuntu 26.10util-linuxpkg:deb/ubuntu/util-linux?arch=source&distro=stonkingOther threatsAffected
  • =2.41.3-3ubuntu2
  • =2.42.2-1ubuntu2
Fixed in–
Ubuntu 26.04 LTSutil-linuxpkg:deb/ubuntu/util-linux?arch=source&distro=resoluteOther threatsAffected
  • 2.41-4ubuntu4 – 2.41.3-3ubuntu2.2
7 affected builds
Fixed in–
Ubuntu Pro 20.04 LTSutil-linuxpkg:deb/ubuntu/util-linux?arch=source&distro=esm-infra/focalOther threatsAffected
  • 2.34-0.1ubuntu2 – 2.34-0.1ubuntu9.6+esm1
13 affected builds
Fixed in–
Ubuntu 18.04 LTSutil-linuxpkg:deb/ubuntu/util-linux?arch=source&distro=bionicOther threatsAffected
  • 2.30.1-0ubuntu4 – 2.31.1-0.4ubuntu3.7
13 affected builds
Fixed in–
Ubuntu Pro 16.04 LTSutil-linuxpkg:deb/ubuntu/util-linux?arch=source&distro=esm-infra/xenialOther threatsAffected
  • 2.26.2-6ubuntu3 – 2.27.1-6ubuntu3.10+esm2
20 affected builds
Fixed in–
Ubuntu 14.04 LTSutil-linuxpkg:deb/ubuntu/util-linux?arch=source&distro=trustyOther threatsAffected
  • 2.20.1-5.1ubuntu9 – 2.20.1-5.1ubuntu20.9
19 affected builds
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

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