---
id: CVE-2026-78408
title: >-
  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()
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 t…
severity: high
cvss: 7.9
cvssVector: 'CVSS:3.1/AV:L/AC:L/PR:L/UI:R/S:C/C:N/I:H/A:H'
cwe:
  - CWE-775
published: '2026-09-02'
updated: '2026-09-05'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-78408'
references:
  - url: 'https://access.redhat.com/errata/RHSA-2026:63162'
    label: secalert@redhat.com
  - url: 'https://access.redhat.com/security/cve/CVE-2026-78408'
    label: secalert@redhat.com
  - url: 'https://bugzilla.redhat.com/show_bug.cgi?id=2522497'
    label: secalert@redhat.com
  - url: >-
      https://github.com/util-linux/util-linux/security/advisories/GHSA-55fx-f4gg-cfhj
    label: secalert@redhat.com
  - url: 'http://www.openwall.com/lists/oss-security/2026/09/05/2'
    label: af854a3a-2127-422b-91ae-364da2661108
  - url: >-
      https://github.com/util-linux/util-linux/security/advisories/GHSA-55fx-f4gg-cfhj
    label: 134c704f-9b21-4f2e-91b3-4a467353bcc0
tags:
  - nvd
epss: 0.00165
epssPercentile: 0.05013
ingestedAt: '2026-09-05T20:44:35.182Z'
---

## Overview

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.

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.