CVE intelligence

CVE-2026-78408

Vulnerability intelligence

Published Sep 2, 2026Sources checked Oct 28, 2026

7.9HIGHCVSS out of 10

What this means

Review the available evidence

CVE-2026-78408 and is rated High severity with a CVSS score of 7.9. It is not in the current CISA KEV record we collected. That does not prove exploitation has not occurred.

What to do next

Remediation and response

Microsoft Security Response Center guidance

Vendor revision: Sep 19, 2026

See the Microsoft Security Update Guide for the update that applies to your product.

Vendor-listed releases

2.40.2-6

CISA KEVNot listedBased on the latest collected catalog

EPSS0.2%Estimated 30-day exploitation probability

Ransomware useNot markedCISA KEV ransomware field

Threat actors0Source-linked actor relationships

Overview

What is CVE-2026-78408?

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.

Source: NVD