CVE-2026-78408
HIGH 7.9 PoC AVAILABLEThe 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.
Public exploit or PoC code exists. Modeled probability is still low, but the barrier to attack is reduced — watch closely.
Exploitation likelihood
0.1%chance of exploitation in 30 days · 2nd percentile
Impact if exploited
7.9CVSS 3.1 · HIGH
- ConfidentialityNone
- IntegrityHigh
- AvailabilityHigh
What an attacker needs
- ⚠Access: Requires local access to the host
- ⚠Privileges: Requires a low-privilege account
- ⚠User interaction: A user must take an action (click / open a file)
- ✓Complexity: No special conditions — reliably repeatable
✓ lowers the bar for an attacker · ⚠ raises it
Proof of concept & exploit code
- reference https://github.com/util-linux/util-linux/security/advisories/GHSA-55fx-f4gg-cfhj
- github-search Search GitHub for public PoC repos
Test against your own equipment
curl -s https://vulnpedia.com/cve/CVE-2026-78408/poc.jsonMachine-readable PoC index for this CVE (for automation).Listed for defensive triage, patch verification, and authorized testing on systems you own. Machine-readable: /cve/CVE-2026-78408/poc.json
Affected
Vendors Red Hat
Products Red Hat Hardened Images Red Hat Enterprise Linux 10 Red Hat Enterprise Linux 7 Red Hat Enterprise Linux 8 Red Hat Enterprise Linux 9 Red Hat Openshift Container Platform 4
Weakness (CWE)
- CWE-775: Missing Release of File Descriptor or Handle after Effective Lifetime
CVSS vector
CVSS:3.1/AV:L/AC:L/PR:L/UI:R/S:C/C:N/I:H/A:H
All CVSS metrics
- HIGH 7.9 v3.1 · CNA Primary
CVSS:3.1/AV:L/AC:L/PR:L/UI:R/S:C/C:N/I:H/A:H - HIGH 7.9 v3.1 · NVD Secondary
CVSS:3.1/AV:L/AC:L/PR:L/UI:R/S:C/C:N/I:H/A:H