CVE-2023-5408
📋 TL;DR
CVE-2023-5408 is a privilege escalation vulnerability in OpenShift's Kubernetes API server node restriction admission plugin. A remote attacker who can modify node role labels could redirect workloads from control plane and etcd nodes to worker nodes, gaining broader cluster access. This affects OpenShift clusters with the node restriction admission plugin enabled.
💻 Affected Systems
- OpenShift Container Platform
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Attacker gains full administrative control over the Kubernetes cluster, allowing them to deploy malicious pods, exfiltrate sensitive data, disrupt cluster operations, or pivot to other systems.
Likely Case
Attacker gains elevated privileges to access worker node resources, potentially compromising applications, stealing credentials, or deploying unauthorized workloads.
If Mitigated
With proper network segmentation, RBAC controls, and monitoring, impact is limited to specific namespaces or workloads, with quick detection and containment.
🎯 Exploit Status
Exploitation requires authenticated access to modify node labels and knowledge of Kubernetes/OpenShift internals.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: OpenShift 4.12.19, 4.13.6, 4.14.1 and later
Vendor Advisory: https://access.redhat.com/security/cve/CVE-2023-5408
Restart Required: Yes
Instructions:
1. Update OpenShift cluster using 'oc adm upgrade' or OpenShift Console. 2. Apply patches for affected versions. 3. Restart API server components after patching.
🔧 Temporary Workarounds
Disable Node Restriction Admission Plugin
linuxTemporarily disable the vulnerable admission plugin (not recommended for production).
oc edit kubeapiserver cluster
Modify spec.unsupportedConfigOverrides to disable NodeRestriction
Restrict Node Label Modification
linuxUse RBAC to restrict who can modify node labels.
oc create clusterrole no-node-label-modify --verb=update,patch --resource=nodes
oc adm policy add-cluster-role-to-user no-node-label-modify -z default
🧯 If You Can't Patch
- Implement strict RBAC controls to limit who can modify node labels and roles.
- Deploy network policies to isolate control plane nodes and monitor for suspicious label changes.
🔍 How to Verify
Check if Vulnerable:
Check OpenShift version with 'oc version' or 'oc get clusterversion'. If version is between affected ranges, system is vulnerable.Check Version:
oc versionVerify Fix Applied:
Verify patch is applied by checking cluster version is 4.12.19+, 4.13.6+, or 4.14.1+ and that node restriction admission plugin is functioning.📡 Detection & Monitoring
Log Indicators:
- Unauthorized node label modifications in API server logs
- Unexpected workload scheduling to worker nodes from control plane
Network Indicators:
- Unusual API calls to modify node resources
- Traffic from worker nodes accessing control plane services
SIEM Query:
source="openshift-api-server" AND (message="Node label update" OR message="Unauthorized node modification")🔗 References
- https://access.redhat.com/errata/RHSA-2023:5006
- https://access.redhat.com/errata/RHSA-2023:6130
- https://access.redhat.com/errata/RHSA-2023:6842
- https://access.redhat.com/errata/RHSA-2023:7479
- https://access.redhat.com/security/cve/CVE-2023-5408
- https://bugzilla.redhat.com/show_bug.cgi?id=2242173
- https://github.com/openshift/kubernetes/pull/1736
- https://access.redhat.com/errata/RHSA-2023:5006
- https://access.redhat.com/errata/RHSA-2023:6130
- https://access.redhat.com/errata/RHSA-2023:6842
- https://access.redhat.com/errata/RHSA-2023:7479
- https://access.redhat.com/security/cve/CVE-2023-5408
- https://bugzilla.redhat.com/show_bug.cgi?id=2242173
- https://github.com/openshift/kubernetes/pull/1736
