scanning-container-security

Scanning Container Security

Overview

Scan container images and Dockerfiles for vulnerabilities, misconfigurations, and compliance violations using Trivy, Grype, Snyk Container, and Hadolint. Analyze base images, OS packages, application dependencies, and runtime configurations to produce actionable security reports with remediation guidance.

Prerequisites

• Container scanning tool installed: trivy, grype, snyk, or docker scout
• Dockerfile linter: hadolint for Dockerfile best practice validation
• Docker daemon running for local image scanning
• Access to the container images to scan (local, registry, or tar archive)
• jq for parsing JSON scan results

Instructions

1. Identify target images for scanning: production images, base images, and CI-built images
2. Lint Dockerfiles with hadolint Dockerfile to catch misconfigurations before build (privileged instructions, pinned versions, shell best practices)
3. Scan built images for OS-level vulnerabilities: trivy image <image:tag> or grype <image:tag>
4. Scan for application dependency vulnerabilities: check language-specific packages (npm, pip, Maven, Go modules) embedded in the image
5. Check for secrets accidentally baked into image layers: trivy image --scanners secret <image:tag>
6. Evaluate image against CIS Docker Benchmark: verify non-root user, read-only filesystem capability, health checks defined
7. Generate a security report with severity classification (Critical, High, Medium, Low) and CVE identifiers
8. Produce remediation steps: upgrade base image, pin package versions, replace vulnerable dependencies
9. Integrate scanning into CI/CD pipeline: fail builds on Critical/High vulnerabilities, generate SARIF output for GitHub Security tab

Output

• Vulnerability scan report in JSON, table, or SARIF format
• Hadolint report with Dockerfile improvement recommendations
• Remediation Dockerfile patches (updated base image, pinned package versions)
• CI/CD pipeline step configuration for automated image scanning
• Security policy document defining acceptable risk thresholds

Error Handling

Error	Cause	Solution
trivy: unable to pull image	Image not found locally or registry auth failure	Pull image first with docker pull or configure registry credentials
CRITICAL vulnerability found but no fix available	Upstream package has no patch yet	Document as accepted risk, use --ignore-unfixed flag, or switch to an alternative base image
hadolint: DL3008 pin versions in apt-get install	Packages installed without version pinning	Add version pins (e.g., apt-get install nginx=1.24.0-1) or use --no-install-recommends
Scan timeout on large image	Image has many layers or large filesystem	Use --timeout 15m flag; scan a specific layer or use --skip-dirs to exclude test data
False positive CVE	Scanner database maps CVE to a package not actually exploitable	Add to .trivyignore or Grype ignore file with justification comment

Examples

• "Scan all production Docker images for Critical and High CVEs, generate a report, and create Jira tickets for each finding."
• "Lint the Dockerfile for best practices: ensure multi-stage build, non-root USER, no ADD for remote URLs, and pinned base image digest."
• "Set up a GitHub Actions step that runs Trivy on every PR, fails on Critical vulnerabilities, and uploads results to the Security tab via SARIF."

Resources

• Trivy: https://aquasecurity.github.io/trivy/
• Grype: https://github.com/anchore/grype
• Hadolint: https://github.com/hadolint/hadolint
• Docker Scout: https://docs.docker.com/scout/
• CIS Docker Benchmark: https://www.cisecurity.org/benchmark/docker