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.
Published: 2026-09-02
Score: 7.9 High
EPSS: < 1% Very Low
KEV: No
Impact: n/a
Action: n/a
AI Analysis

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Remediation

Vendor Workaround

Upgrade to util-linux v2.41.6, v2.42.3, or later. Until a fix is applied, do not run nsenter --join-cgroup (including nsenter --target PID --all --join-cgroup) against untrusted processes or namespaces. The fix closes the cgroup.procs descriptor immediately after joining, and opens it with O_CLOEXEC.

Tracking

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History

Thu, 03 Sep 2026 16:45:00 +0000

Type Values Removed Values Added
First Time appeared Linux
Linux util-linux
Redhat hardened Images
Redhat openshift Container Platform
Vendors & Products Linux
Linux util-linux
Redhat hardened Images
Redhat openshift Container Platform

Thu, 03 Sep 2026 13:00:00 +0000

Type Values Removed Values Added
References

Thu, 03 Sep 2026 12:15:00 +0000

Type Values Removed Values Added
References
Metrics threat_severity

None

threat_severity

Important


Wed, 02 Sep 2026 10:45:00 +0000

Type Values Removed Values Added
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.
Title Util-linux: util-linux: nsenter --join-cgroup leaks root cgroup migration authority
First Time appeared Redhat
Redhat enterprise Linux
Redhat hummingbird
Redhat openshift
Weaknesses CWE-775
CPEs cpe:/a:redhat:hummingbird:1
cpe:/a:redhat:openshift:4
cpe:/o:redhat:enterprise_linux:10
cpe:/o:redhat:enterprise_linux:7
cpe:/o:redhat:enterprise_linux:8
cpe:/o:redhat:enterprise_linux:9
Vendors & Products Redhat
Redhat enterprise Linux
Redhat hummingbird
Redhat openshift
References
Metrics cvssV3_1

{'score': 7.9, 'vector': 'CVSS:3.1/AV:L/AC:L/PR:L/UI:R/S:C/C:N/I:H/A:H'}


Subscriptions

Linux Util-linux
Redhat Enterprise Linux Hardened Images Hummingbird Openshift Openshift Container Platform
cve-icon MITRE

Status: PUBLISHED

Assigner: redhat

Published:

Updated: 2026-09-03T12:50:51.689Z

Reserved: 2026-08-24T14:40:14.511Z

Link: CVE-2026-78408

cve-icon Vulnrichment

No data.

cve-icon NVD

Status : Awaiting Analysis

Published: 2026-09-02T16:17:23.687

Modified: 2026-09-03T18:12:56.407

Link: CVE-2026-78408

cve-icon Redhat

Severity : Important

Publid Date: 2026-09-02T00:00:00Z

Links: CVE-2026-78408 - Bugzilla

cve-icon OpenCVE Enrichment

Updated: 2026-09-03T16:27:19Z

Weaknesses