scanning-container-images-with-grype

Scanning Container Images with Grype

Overview

Grype is an open-source vulnerability scanner from Anchore that inspects container images, filesystems, and SBOMs for known CVEs. It leverages Syft-generated SBOMs to match packages against multiple vulnerability databases including NVD, GitHub Advisories, and OS-specific feeds.

When to Use

• When conducting security assessments that involve scanning container images with grype
• 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

• Docker or Podman installed
• Grype CLI installed (curl -sSfL https://raw.githubusercontent.com/anchore/grype/main/install.sh | sh -s -- -b /usr/local/bin)
• Syft CLI (optional, for SBOM generation)
• Network access to pull vulnerability databases

Core Commands

Install Grype

# Install via script
curl -sSfL https://raw.githubusercontent.com/anchore/grype/main/install.sh | sh -s -- -b /usr/local/bin

# Verify installation
grype version

# Install via Homebrew (macOS/Linux)
brew install grype

Scan Container Images

# Scan a Docker Hub image
grype nginx:latest

# Scan from Docker daemon
grype docker:myapp:1.0

# Scan a local archive
grype docker-archive:image.tar

# Scan an OCI directory
grype oci-dir:path/to/oci/

# Scan a Singularity image
grype sif:image.sif

# Scan a local directory / filesystem
grype dir:/path/to/project

Output Formats

# Default table output
grype alpine:3.18

# JSON output for pipeline processing
grype alpine:3.18 -o json > results.json

# CycloneDX SBOM output
grype alpine:3.18 -o cyclonedx

# SARIF output for GitHub Security tab
grype alpine:3.18 -o sarif > grype.sarif

# Template-based custom output
grype alpine:3.18 -o template -t /path/to/template.tmpl

Filtering and Thresholds

# Fail if vulnerabilities meet or exceed a severity
grype nginx:latest --fail-on critical

# Show only fixed vulnerabilities
grype nginx:latest --only-fixed

# Show only non-fixed vulnerabilities
grype nginx:latest --only-notfixed

# Filter by severity
grype nginx:latest --only-fixed -o json | jq '[.matches[] | select(.vulnerability.severity == "High")]'

# Explain a specific CVE
grype nginx:latest --explain --id CVE-2024-1234

Working with SBOMs

# Generate SBOM with Syft then scan
syft nginx:latest -o spdx-json > nginx-sbom.json
grype sbom:nginx-sbom.json

# Scan CycloneDX SBOM
grype sbom:bom.json

Configuration File (.grype.yaml)

# .grype.yaml
check-for-app-update: false
fail-on-severity: "high"
output: "json"
scope: "squashed"  # or "all-layers"
quiet: false

ignore:
  - vulnerability: CVE-2023-12345
    reason: "False positive - not exploitable in our context"
  - vulnerability: CVE-2023-67890
    fix-state: unknown

db:
  auto-update: true
  cache-dir: "/tmp/grype-db"
  max-allowed-built-age: 120h  # 5 days

match:
  java:
    using-cpes: true
  python:
    using-cpes: true
  javascript:
    using-cpes: false

CI/CD Integration

# GitHub Actions
- name: Scan image with Grype
  uses: anchore/scan-action@v4
  with:
    image: "myregistry/myapp:${{ github.sha }}"
    fail-build: true
    severity-cutoff: high
    output-format: sarif
  id: scan

- name: Upload SARIF
  uses: github/codeql-action/upload-sarif@v3
  with:
    sarif_file: ${{ steps.scan.outputs.sarif }}

# GitLab CI
container_scan:
  stage: test
  image: anchore/grype:latest
  script:
    - grype ${CI_REGISTRY_IMAGE}:${CI_COMMIT_SHA} --fail-on high -o json > grype-report.json
  artifacts:
    reports:
      container_scanning: grype-report.json

Database Management

# Check database status
grype db status

# Manually update vulnerability database
grype db update

# Delete cached database
grype db delete

# List supported database providers
grype db list

Key Vulnerability Sources

Source	Coverage
NVD	CVEs across all ecosystems
GitHub Advisories	Open source package vulnerabilities
Alpine SecDB	Alpine Linux packages
Amazon Linux ALAS	Amazon Linux AMI
Debian Security Tracker	Debian packages
Red Hat OVAL	RHEL, CentOS
Ubuntu Security	Ubuntu packages
Wolfi SecDB	Wolfi/Chainguard images

Best Practices

1. Pin image tags - Always scan specific digests, not latest
2. Fail on severity - Set --fail-on high or critical in CI gates
3. Use SBOMs - Generate SBOMs with Syft for reproducible scanning
4. Suppress false positives - Use .grype.yaml ignore rules with documented reasons
5. Scan all layers - Use --scope all-layers to catch vulnerabilities in intermediate layers
6. Automate database updates - Keep the vulnerability database current in CI runners
7. Compare scans - Track vulnerability count over time for regression detection