Key Takeaways
- Common container security vulnerabilities persist because they are checked in isolation, not across the full container lifecycle
- Image scans miss runtime drift, privilege changes, and rogue containers in production environments
- Ephemeral containers outpace scheduled scans, leaving gaps in visibility and detection
- Continuous monitoring, least privilege, and runtime security are essential for reducing risk
- Unified visibility across container, host, and cloud layers is critical to maintaining a strong security posture
The list hasn’t changed. The failures haven’t either.
Outdated images. Root containers. Exposed Kubernetes API servers. Hardcoded secrets. These are still the most common container security vulnerabilities, year after year, across containerized applications of every size.
What’s more useful than the list itself is the second half of it: why these same issues keep slipping past security teams that already scan, patch, and monitor. Below, each vulnerability comes with the reason it’s so often missed, not just the fix.
What Are the Most Common Container Security Vulnerabilities?
Most container security risks fall into two buckets: baked into the image before it runs, or only visible once it’s live in a production environment. Here’s both halves, side by side.
| Vulnerability | What It Is | Why It's Often Missed |
|---|---|---|
| Outdated base images | Inherited CVEs from OS packages in the base layer | The image gets scanned once, then sits in a registry for months while new CVEs pile up |
| Hardcoded secrets in image layers | Credentials written in one layer, "removed" in the next | Still recoverable from layer history; nothing in the running container shows it |
| Containers running as root | No separation between container privileges and host privileges | Treated as a configuration detail, not a deployment gate |
| Excessive capabilities or --privileged | Near-full access to the host kernel | Set during early development and never revisited before going live |
| Untrusted or unverified registries | Images pulled from outside the approved pipeline | Convenience pulls during dev or troubleshooting bypass review entirely |
| Container escape (e.g., CVE-2024-21626) | A process breaks out of the container into the host filesystem | Teams patch application images regularly, runc and containerd far less often |
| Exposed Kubernetes API server | Control plane reachable without strong authentication | Managed Kubernetes creates a false sense that the cloud provider handles this |
| No network segmentation / rogue containers | Lateral movement and unauthorized containers blending in | No baseline of "what should be running" to compare against |
Two of these are worth a closer look, because the scale is easy to underestimate.
CVE-2024-216261, the “Leaky Vessels” runc flaw, let a newly started container’s working directory point into the host filesystem, giving an attacker the ability to read host files and, in some cases, execute arbitrary code on the host operating system itself. It affected runc up to 1.1.11, containerd before 1.6.28/1.7.13, and Docker before 25.0.2. That’s most of the container ecosystem, all at once.
On the API server side, RedHunt Labs’ Project2 Resonance scanned the internet and found over half a million misconfigured, internet-facing Kubernetes components, more than 338,000 of them exposed API servers, a sizable chunk of the public attack surface on its own. The CISA/NSA Kubernetes Hardening Guide3 treats locking this down as a baseline, not an advanced step.
- The 2026 Cloud Security Reality
- Security Across the Full Lifecycle: Code to Runtime
- Compliance Without the Last-minute Scramble
Why Are Container Security Vulnerabilities So Often Missed?
None of these vulnerabilities are individually hard to fix. What makes them persistent is when and how they get checked across container infrastructure.
Scans Run Too Late for Dynamic Containers
A weekly or nightly scan assumes the thing being scanned is still around when results come back. In an auto-scaling cluster, the running containers have often already been replaced.
Image Security Doesn’t Reflect Runtime Reality
An image can pass every check before deployment, then pick up extra capabilities, mounts, or privileges once an orchestrator schedules it. Static checks never see that drift between the image and the running container.
Security Data Is Split Across Tools
A vulnerability flagged in an image scan and a misconfiguration flagged in a cloud posture tool can describe the same security issue without anyone connecting the two. The data lives in separate places, often owned by separate teams with separate access management.
Put together, these three patterns explain most of the gap between “we scan our containers” and “we still had a security incident through a container.”
What Are the Best Practices for Container Security?
Every row in the table above traces back to one of four container security best practices. None of these are exotic. The gap is usually consistency, not awareness.
Enforce Least Privilege by Default
Run containers as non-root, drop unused Linux capabilities, and skip –privileged unless there’s no other option. Least privilege removes the shortest path from a compromised container to the host operating system.
Scan Continuously, Not Just at Build Time
A clean scan before an image is pushed doesn’t mean the image is clean by the time it’s deployed weeks later. Run container scanning tools again at deploy time, and treat the results as ongoing container vulnerability management rather than a one-time gate.
Monitor Continuously for Drift
Scheduled scans match a calendar, not a cluster. Continuous monitoring catches the drift between what was approved and what’s actually running, which is where most container vulnerabilities end up living undetected.
Secure Containers at Runtime
Image scans can’t see a container escape or a rogue container after deployment. Runtime security covers that gap, and network segmentation with default-deny policies limits how far a compromised container can reach if something does get through.
- Automate Security Across the Container Stack
- Extensive Compliance Controls
- Cloud-native and Integrated
How Does Fidelis Halo Container Secure Help Close These Gaps?
Closing the gap means the same checks running across image, runtime, host, and cloud account, on a continuous basis rather than a scheduled one. Fidelis Halo Container Secure, part of the Fidelis CloudPassage Halo platform, is built around that idea.
On the image side, registry connectors scan images at rest and check images as they’re pushed, with pass/fail gates that plug into CI tools like Jenkins. That addresses the “scanned once, then forgotten” problem directly.
At runtime, it tracks container instances and Kubernetes services against their configuration, capabilities, namespaces, and security options, flagging containers that don’t match an approved image. Rogue containers can be quarantined within seconds, which is the missing baseline most containerized environments don’t have.
On the host side, a small microagent (about 2MB, for Linux and Windows, or deployed as a Kubernetes DaemonSet) covers the Docker hosts and Kubernetes nodes underneath, with file integrity monitoring and drift detection. The policy set is built on CIS Benchmarks, PCI, HIPAA, and SOC 2, and updates automatically to support ongoing compliance.
Findings route through a REST API into Jira, Slack, or ServiceNow, so they land where teams already work instead of a separate dashboard. And because Fidelis Cloud Secure provides agentless CSPM for AWS, Azure, and GCP under the same platform, an exposed API server or over-permissioned IAM role gets assessed alongside container and host findings, not in a different tool entirely.
That’s the practical version of closing the gap: one set of checks, run continuously, across every layer of container infrastructure where these vulnerabilities actually live.
Frequently Asked Questions
Why does a scanned image still end up vulnerable in production?
Because the scan is a snapshot. New CVEs get published daily, and an image that was clean at build time can be carrying known vulnerabilities by the time it’s actually deployed weeks later.
Is an exposed Kubernetes API server really that common?
Yes. Internet-wide scans regularly find hundreds of thousands of exposed API servers and kubelet endpoints, often on managed Kubernetes clusters where teams assumed the cloud provider had locked it down.
Does passing a CIS Benchmark mean the environment is secure?
It means the configuration was correct at the time it was checked. It doesn’t confirm a running container still matches that configuration, or that nothing new has been deployed since.
What's the fastest way to catch a rogue container?
Continuously compare what’s running against the approved image source. Without that baseline, a rogue container can sit unnoticed indefinitely.
Are containers less secure than virtual machines?
Not inherently, but they fail differently. Virtual machines each run their own kernel, so a flaw in one rarely reaches the others. Containers share the host’s kernel, so a container escape or kernel exploit can affect every container on that host at once.
What's the difference between container security and Kubernetes security?
Kubernetes security covers the orchestrator: RBAC, network policies, the API server, and access control across the cluster. Container security is broader and includes the image, the registry, the runtime, and the host operating system underneath. The two overlap heavily but aren’t the same thing.
