Scanning Kubernetes Manifests with Kubesec
Overview
Kubesec is an open-source security risk analysis tool developed by ControlPlane that inspects Kubernetes resource manifests for common exploitable risks such as privilege escalation, writable host mounts, and excessive capabilities. It assigns a numerical security score to each resource and provides actionable recommendations for hardening. Kubesec can be used as a CLI binary, Docker container, kubectl plugin, admission webhook, or REST API endpoint.
When to Use
- When conducting security assessments that involve scanning kubernetes manifests with kubesec
- When following incident response procedures for related security events
- When performing scheduled security testing or auditing activities
- When validating security controls through hands-on testing
Prerequisites
- Kubernetes manifest files (YAML/JSON) for Deployments, Pods, DaemonSets, StatefulSets
- Docker or Go runtime for local installation
- kubectl access for scanning live cluster resources
- CI/CD pipeline access for automated scanning integration
Core Concepts
Security Scoring System
Kubesec assigns a score to each Kubernetes resource based on security checks:
- Positive scores: Awarded for security-enhancing configurations (readOnlyRootFilesystem, runAsNonRoot)
- Zero or negative scores: Indicate missing security controls or dangerous configurations
- Critical advisories: Flagged configurations that represent immediate security risks
Check Categories
- Privilege Controls: Checks for privileged containers, host PID/network access, root execution
- Capabilities: Identifies excessive Linux capabilities (SYS_ADMIN, NET_RAW)
- Volume Mounts: Detects dangerous host path mounts and writable sensitive paths
- Resource Limits: Validates presence of CPU/memory resource constraints
- Security Context: Verifies seccomp profiles, AppArmor annotations, SELinux contexts
Installation
Binary Installation
# Linux/macOS
curl -sSL https://github.com/controlplaneio/kubesec/releases/latest/download/kubesec_linux_amd64.tar.gz | \
tar xz -C /usr/local/bin/ kubesec
# Verify installation
kubesec version
Docker Installation
docker pull kubesec/kubesec:v2
# Scan a manifest file
docker run -i kubesec/kubesec:v2 scan /dev/stdin < deployment.yaml
kubectl Plugin
kubectl krew install kubesec-scan
kubectl kubesec-scan pod mypod -n default
Practical Scanning
Scanning a Single Manifest
# Scan a deployment manifest
kubesec scan deployment.yaml
# Scan with JSON output
kubesec scan -o json deployment.yaml
# Scan from stdin
cat pod.yaml | kubesec scan -
Sample Output
[
{
"object": "Pod/web-app.default",
"valid": true,
"fileName": "pod.yaml",
"message": "Passed with a score of 3 points",
"score": 3,
"scoring": {
"passed": [
{
"id": "ReadOnlyRootFilesystem",
"selector": "containers[] .securityContext .readOnlyRootFilesystem == true",
"reason": "An immutable root filesystem prevents applications from writing to their local disk",
"points": 1
},
{
"id": "RunAsNonRoot",
"selector": "containers[] .securityContext .runAsNonRoot == true",
"reason": "Force the running image to run as a non-root user",
"points": 1
},
{
"id": "LimitsCPU",
"selector": "containers[] .resources .limits .cpu",
"reason": "Enforcing CPU limits prevents DOS via resource exhaustion",
"points": 1
}
],
"advise": [
{
"id": "ApparmorAny",
"selector": "metadata .annotations .\"container.apparmor.security.beta.kubernetes.io/nginx\"",
"reason": "Well defined AppArmor policies reduce the attack surface of the container",
"points": 3
},
{
"id": "ServiceAccountName",
"selector": ".spec .serviceAccountName",
"reason": "Service accounts restrict Kubernetes API access and should be configured",
"points": 3
}
]
}
}
]
Scanning Multiple Resources
# Scan all YAML files in a directory
for file in manifests/*.yaml; do
echo "=== Scanning $file ==="
kubesec scan "$file"
done
# Scan multi-document YAML
kubesec scan multi-resource.yaml
Using the HTTP API
# Scan via the public API
curl -sSX POST --data-binary @deployment.yaml \
https://v2.kubesec.io/scan
# Run a local API server
kubesec http --port 8080 &
# Scan against local server
curl -sSX POST --data-binary @deployment.yaml \
http://localhost:8080/scan
CI/CD Integration
GitHub Actions
name: Kubesec Scan
on: [pull_request]
jobs:
kubesec:
runs-on: ubuntu-latest
steps:
- uses: actions/checkout@v4
- name: Install Kubesec
run: |
curl -sSL https://github.com/controlplaneio/kubesec/releases/latest/download/kubesec_linux_amd64.tar.gz | \
tar xz -C /usr/local/bin/ kubesec
- name: Scan Manifests
run: |
FAIL=0
for file in k8s/*.yaml; do
SCORE=$(kubesec scan "$file" | jq '.[0].score')
echo "$file: score=$SCORE"
if [ "$SCORE" -lt 0 ]; then
echo "FAIL: $file has critical issues (score: $SCORE)"
FAIL=1
fi
done
exit $FAIL
GitLab CI
kubesec-scan:
stage: security
image: kubesec/kubesec:v2
script:
- |
for file in k8s/*.yaml; do
kubesec scan "$file" > /tmp/result.json
SCORE=$(cat /tmp/result.json | jq '.[0].score')
if [ "$SCORE" -lt 0 ]; then
echo "CRITICAL: $file scored $SCORE"
cat /tmp/result.json | jq '.[0].scoring.critical'
exit 1
fi
done
artifacts:
paths:
- kubesec-results/
Admission Webhook
Deploy Kubesec as a ValidatingWebhookConfiguration to reject insecure manifests at deploy time:
apiVersion: admissionregistration.k8s.io/v1
kind: ValidatingWebhookConfiguration
metadata:
name: kubesec-webhook
webhooks:
- name: kubesec.controlplane.io
rules:
- apiGroups: [""]
apiVersions: ["v1"]
operations: ["CREATE", "UPDATE"]
resources: ["pods"]
- apiGroups: ["apps"]
apiVersions: ["v1"]
operations: ["CREATE", "UPDATE"]
resources: ["deployments", "daemonsets", "statefulsets"]
clientConfig:
service:
name: kubesec-webhook
namespace: kube-system
path: /scan
failurePolicy: Fail
sideEffects: None
admissionReviewVersions: ["v1"]
Security Checks Reference
Critical Checks (Negative Score)
| Check | Selector | Risk |
|---|---|---|
| Privileged | securityContext.privileged == true |
Full host access |
| HostPID | spec.hostPID == true |
Process namespace escape |
| HostNetwork | spec.hostNetwork == true |
Network namespace escape |
| SYS_ADMIN | capabilities.add contains SYS_ADMIN |
Near-root capability |
Best Practice Checks (Positive Score)
| Check | Points | Description |
|---|---|---|
| ReadOnlyRootFilesystem | +1 | Prevents filesystem writes |
| RunAsNonRoot | +1 | Non-root process execution |
| RunAsUser > 10000 | +1 | High UID reduces collision risk |
| LimitsCPU | +1 | Prevents CPU resource exhaustion |
| LimitsMemory | +1 | Prevents memory resource exhaustion |
| RequestsCPU | +1 | Ensures scheduler resource awareness |
| ServiceAccountName | +3 | Explicit service account |
| AppArmor annotation | +3 | Kernel-level MAC enforcement |
| Seccomp profile | +4 | Syscall filtering |