Container Vulnerability Scanning with Grype

Overview

Grype is an open-source vulnerability scanner that identifies known security flaws in container images, filesystems, and Software Bill of Materials (SBOM) documents. It analyzes operating system packages (Alpine, Ubuntu, Red Hat, Debian) and language-specific dependencies (Java, Python, JavaScript, Ruby, Go, PHP, Rust) against vulnerability databases to detect CVEs.

Grype emphasizes actionable security insights through:

• CVSS severity ratings for risk classification
• EPSS exploit probability scores for threat assessment
• CISA Known Exploited Vulnerabilities (KEV) indicators
• Multiple output formats (table, JSON, SARIF, CycloneDX) for toolchain integration

Quick Start

Scan a container image:

grype <image-name>

Examples:

# Scan official Docker image
grype alpine:latest

# Scan local Docker image
grype myapp:v1.2.3

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

# Scan SBOM file
grype sbom:/path/to/sbom.json

Core Workflow

Basic Vulnerability Scan

1. Identify scan target: Determine what to scan (container image, filesystem, SBOM)
2. Run Grype scan: Execute grype <target> to analyze for vulnerabilities
3. Review findings: Examine CVE IDs, severity, CVSS scores, affected packages
4. Prioritize remediation: Focus on critical/high severity, CISA KEV, high EPSS scores
5. Apply fixes: Update vulnerable packages or base images
6. Re-scan: Verify vulnerabilities are resolved

CI/CD Integration with Fail Thresholds

For automated pipeline security gates:

# Fail build if any critical vulnerabilities found
grype <image> --fail-on critical

# Fail on high or critical severities
grype <image> --fail-on high

# Output JSON for further processing
grype <image> -o json > results.json

Pipeline integration pattern:

1. Build container image
2. Run Grype scan with --fail-on threshold
3. If scan fails: Block deployment, alert security team
4. If scan passes: Continue deployment workflow
5. Archive scan results as build artifacts

SBOM-Based Scanning

Use Grype with Syft-generated SBOMs for faster re-scanning:

# Generate SBOM with Syft (separate skill: sbom-syft)
syft <image> -o json > sbom.json

# Scan SBOM with Grype (faster than re-analyzing image)
grype sbom:sbom.json

# Pipe Syft output directly to Grype
syft <image> -o json | grype

Benefits of SBOM workflow:

• Faster re-scans without re-analyzing image layers
• Share SBOMs across security tools
• Archive SBOMs for compliance and auditing

Risk Prioritization Workflow

Progress: [ ] 1. Run full Grype scan with JSON output: grype <target> -o json > results.json [ ] 2. Use helper script to extract high-risk CVEs: ./scripts/prioritize_cves.py results.json [ ] 3. Review CISA KEV matches (actively exploited vulnerabilities) [ ] 4. Check EPSS scores (exploit probability) for non-KEV findings [ ] 5. Prioritize remediation: KEV > High EPSS > CVSS Critical > CVSS High [ ] 6. Document remediation plan with CVE IDs and affected packages [ ] 7. Apply fixes and re-scan to verify

Work through each step systematically. Check off completed items.

Output Formats

Grype supports multiple output formats for different use cases:

Table (default): Human-readable console output

grype <image>

JSON: Machine-parseable for automation

grype <image> -o json

SARIF: Static Analysis Results Interchange Format for IDE integration

grype <image> -o sarif

CycloneDX: SBOM format with vulnerability data

grype <image> -o cyclonedx-json

Template: Custom output using Go templates

grype <image> -o template -t custom-template.tmpl

Advanced Configuration

Filtering and Exclusions

Exclude specific file paths:

grype <image> --exclude '/usr/share/doc/**'

Filter by severity:

grype <image> --only-fixed  # Only show vulnerabilities with available fixes

Custom Ignore Rules

Create .grype.yaml to suppress false positives:

ignore:
  # Ignore specific CVE
  - vulnerability: CVE-YYYY-XXXXX
    reason: "False positive - component not used"

  # Ignore CVE for specific package
  - vulnerability: CVE-YYYY-ZZZZZ
    package:
      name: example-lib
      version: 1.2.3
    reason: "Risk accepted - mitigation controls in place"

Database Management

Update vulnerability database:

grype db update

Check database status:

grype db status

Use specific database location:

grype <image> --db /path/to/database

Security Considerations

• Sensitive Data Handling: Scan results may contain package names and versions that reveal application architecture. Store results securely and limit access to authorized security personnel.

• Access Control: Grype requires Docker socket access when scanning container images. Restrict permissions to prevent unauthorized image access.

• Audit Logging: Log all Grype scans with timestamps, target details, and operator identity for compliance and incident response. Archive scan results for historical vulnerability tracking.

• Compliance: Regular vulnerability scanning supports SOC2, PCI-DSS, NIST 800-53, and ISO 27001 requirements. Document scan frequency and remediation SLAs.

• Safe Defaults: Use --fail-on critical as minimum threshold for production deployments. Configure automated scans in CI/CD to prevent vulnerable images from reaching production.

Bundled Resources

Scripts (scripts/)

• prioritize_cves.py - Parse Grype JSON output and prioritize CVEs by threat metrics (KEV, EPSS, CVSS)
• grype_scan.sh - Wrapper script for consistent Grype scans with logging and threshold configuration

References (references/)

• cvss_guide.md - CVSS severity rating system and score interpretation
• cisa_kev.md - CISA Known Exploited Vulnerabilities catalog and remediation urgency
• vulnerability_remediation.md - Common remediation patterns for dependency vulnerabilities

Assets (assets/)

• grype-ci-config.yml - CI/CD pipeline configuration for Grype vulnerability scanning
• grype-config.yaml - Example Grype configuration with common ignore patterns

Common Patterns

Pattern 1: Pre-Production Scanning

Scan before pushing images to registry:

# Build image
docker build -t myapp:latest .

# Scan locally before push
grype myapp:latest --fail-on critical

# If scan passes, push to registry
docker push myapp:latest

Pattern 2: Scheduled Scanning

Re-scan existing images for newly disclosed vulnerabilities:

# Scan all production images daily
for image in $(docker images --format '{{.Repository}}:{{.Tag}}' | grep prod); do
  grype $image -o json >> daily-scan-$(date +%Y%m%d).json
done

Pattern 3: Base Image Selection

Compare base images to choose least vulnerable option:

# Compare Alpine versions
grype alpine:3.18
grype alpine:3.19

# Compare distros
grype ubuntu:22.04
grype debian:12-slim
grype alpine:3.19

Integration Points

• CI/CD: Integrate with GitHub Actions, GitLab CI, Jenkins, CircleCI using --fail-on thresholds
• Container Registries: Scan images from Docker Hub, ECR, GCR, ACR, Harbor
• Security Tools: Export SARIF for GitHub Security, JSON for SIEM ingestion, CycloneDX for DependencyTrack
• SDLC: Scan during build (shift-left), before deployment (quality gate), and scheduled (continuous monitoring)

Troubleshooting

Issue: Database Update Fails

Symptoms: grype db update fails with network errors

Solution:

• Check network connectivity and proxy settings
• Verify firewall allows access to Grype database sources
• Use grype db update --verbose for detailed error messages
• Consider using offline database: grype db import /path/to/database.tar.gz

Issue: False Positives

Symptoms: Grype reports vulnerabilities in unused code or misidentified packages

Solution:

• Create .grype.yaml ignore file with specific CVE suppressions
• Document justification for each ignored vulnerability
• Periodically review ignored CVEs (quarterly) to reassess risk
• Use --only-fixed to focus on actionable findings

Issue: Slow Scans

Symptoms: Grype scans take excessive time on large images

Solution:

• Use SBOM workflow: Generate SBOM once with Syft, re-scan SBOM with Grype
• Exclude unnecessary paths: --exclude '/usr/share/doc/**'
• Use local database cache: grype db update before batch scans
• Scan base images separately to identify inherited vulnerabilities

References

• Grype GitHub Repository
• Grype Documentation
• NIST National Vulnerability Database
• CISA Known Exploited Vulnerabilities
• FIRST EPSS (Exploit Prediction Scoring System)
• CVSS Specification