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Fencer Vulns
high 7.9

CVE-2026-78408 json

Util-linux: util-linux: nsenter --join-cgroup leaks root cgroup migration authority

published 2026-09-02 2 mo ago modified 2026-11-05 4 d ago also EUVD-2026-70105

cvss
7.9
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.2%
EPSS 0.2% chance of exploitation in 30 days, percentile 14%
public exploits
0
none known

Summary

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.

Patch / fix

  • Red Hat Red Hat Enterprise Linux 10 0:2.40.2-18.el10_2.20
  • Red Hat Red Hat Cost Management On-Premise 1 1793825318
  • Red Hat Red Hat Hardened Images 2.42.2-3.4.hum1
  • util-linux Debian 14 2.42.4-1

debian advisories DEBIAN-CVE-2026-78408

  • uuidd hummingbird 1 2.42.2-3.4.hum1
  • libuuid hummingbird 1 2.42.2-3.4.hum1
  • libblkid hummingbird 1 2.42.2-3.4.hum1
  • libfdisk hummingbird 1 2.42.2-3.4.hum1
  • libmount hummingbird 1 2.42.2-3.4.hum1
  • util-linux hummingbird 1 2.42.2-3.4.hum1
  • liblastlog2 hummingbird 1 2.42.2-3.4.hum1
  • libsmartcols hummingbird 1 2.42.2-3.4.hum1

red hat advisories RHSA-2026:63162

  • util-linux SLES 16.0, Linux Micro 6.2, SLES for SAP applications 16.0 2.41.1-160000.5.1
  • python-libmount SLES 16.0, SLES for SAP applications 16.0 2.41.1-160000.5.1
  • util-linux-systemd SLES 16.0, Linux Micro 6.2, SLES for SAP applications 16.0 2.41.1-160000.5.1

suse advisories SUSE-SU-2026:23861-1SUSE-SU-2026:23870-1SUSE-SU-2026:23884-1

  • util-linux openSUSE Tumbleweed 2.42.3-1.1
  • util-linux openSUSE Leap 16.0 2.41.1-160000.5.1
  • python-libmount openSUSE Leap 16.0 2.41.1-160000.5.1
  • util-linux-systemd openSUSE Leap 16.0 2.41.1-160000.5.1

opensuse advisories openSUSE-SU-2026:11870-1openSUSE-SU-2026:21905-1

  • util-linux AlmaLinux 10 2.40.2-18.el10_2.20
  • uuidd AlmaLinux 10 2.40.2-18.el10_2.20
  • libuuid AlmaLinux 10 2.40.2-18.el10_2.20
  • libblkid AlmaLinux 10 2.40.2-18.el10_2.20
  • libfdisk AlmaLinux 10 2.40.2-18.el10_2.20
  • libmount AlmaLinux 10 2.40.2-18.el10_2.20
  • libsmartcols AlmaLinux 10 2.40.2-18.el10_2.20
  • util-linux-core AlmaLinux 10 2.40.2-18.el10_2.20

almalinux advisories ALSA-2026:93461

  • util-linux Rocky Linux 10 2.40.2-18.el10_2.20

rocky linux advisories RLSA-2026:93461

  • util-linux Alpine 3.23, Alpine 3.22 2.41.6-r1
  • util-linux Alpine 3.24 2.42.3-r1

alpine advisories ALPINE-CVE-2026-78408

Alpine secdb © Alpine Linux, from https://secdb.alpinelinux.org via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • util-linux Azure Linux 3.0 2.40.2-6

azure linux advisories AZL-99393

Azure Linux vulnerability data, Copyright (c) Microsoft Corporation, from https://github.com/microsoft/AzureLinuxVulnerabilityData via OSV, under the MIT licence; changed: normalised to fixed package versions per release. MIT

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-78408 updated cvss 7.9

util-linux: util-linux: nsenter --join-cgroup leaks root cgroup migration authority

  • Red Hat Cost Management On-Premise 1 costmanagement/costmanagement-ui-rhel10 1793825318
    fixed: vendor fix RHSA-2026:95365
  • Red Hat Enterprise Linux AppStream (v. 10) uuidd 2.40.2-18.el10_2.20, python3-libmount 2.40.2-18.el10_2.20 Red Hat Enterprise Linux BaseOS (v. 10) libuuid 2.40.2-18.el10_2.20, libblkid 2.40.2-18.el10_2.20, libfdisk 2.40.2-18.el10_2.20, libmount 2.40.2-18.el10_2.20, util-linux 2.40.2-18.el10_2.20, libsmartcols 2.40.2-18.el10_2.20, +1 more Red Hat Enterprise Linux CodeReady Linux Builder (v. 10) libfdisk-devel 2.40.2-18.el10_2.20, uuidd-debuginfo 2.40.2-18.el10_2.20, libuuid-debuginfo 2.40.2-18.el10_2.20, libblkid-debuginfo 2.40.2-18.el10_2.20, libfdisk-debuginfo 2.40.2-18.el10_2.20, libmount-debuginfo 2.40.2-18.el10_2.20, +6 more
    fixed: vendor fix RHSA-2026:93461
  • Red Hat Hardened Images uuidd 2.42.2-3.4.hum1, libuuid 2.42.2-3.4.hum1, libblkid 2.42.2-3.4.hum1, libfdisk 2.42.2-3.4.hum1, libmount 2.42.2-3.4.hum1, util-linux 2.42.2-3.4.hum1, +6 more
    fixed: vendor fix RHSA-2026:63162
  • Red Hat Enterprise Linux 7 uuidd, libuuid, libblkid, libmount, util-linux Red Hat Enterprise Linux 8 uuidd, libuuid, libblkid, libfdisk, libmount, util-linux, +3 more Red Hat Enterprise Linux 9 uuidd, libuuid, libblkid, libfdisk, libmount, util-linux, +6 more Red Hat OpenShift Container Platform 4 openshift/ose-rhel-coreos-8, openshift/ose-rhel-coreos-9 Red Hat OpenShift Container Platform 5 openshift/ose-rhel-coreos-9
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
Proof of concept is public
Automatable
no
Technical impact
partial
Assessed
2 mo ago

Exploit prediction

0.24% chance of exploitation in the next 30 days, higher than 14% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

  • github.com https://github.com/util-linux/util-linux/security/advisories/GHSA-55fx-f4gg-cfhj referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
CNA 3.1 7.9 CVSS:3.1/AV:L/AC:L/PR:L/UI:R/S:C/C:N/I:H/A:H

Affected products

  • Red Hat Red Hat Enterprise Linux 10
  • Red Hat Red Hat Cost Management On-Premise 1
  • Red Hat Red Hat Hardened Images
  • Red Hat Red Hat Enterprise Linux 7
  • Red Hat Red Hat Enterprise Linux 8
  • Red Hat Red Hat Enterprise Linux 9
  • Red Hat Red Hat OpenShift Container Platform 4
  • Red Hat Red Hat OpenShift Container Platform 5

Classification

Weakness
  • CWE-775 Missing Release of File Descriptor or Handle after Effective Lifetime

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.