What Is Semgrep?
A fast, open-source static analysis tool that finds bugs and security vulnerabilities using lightweight pattern matching. Semgrep supports 30+ languages with a simple rule syntax that lets developers write custom security checks. It runs in CI/CD and provides both community-maintained and proprietary rule sets.
Security Risks
Semgrep is primarily a detection tool, with limitations to understand:
- Pattern-based: Catches known patterns but cannot reason about complex business logic
- No runtime analysis: Only analyzes source code, not deployed application behavior
- Rule coverage: Community rules may not cover latest frameworks or AI-specific patterns
- Cross-file analysis: Limited compared to full-featured SAST tools for complex data flows
- Configuration required: Needs rule selection and tuning for each project
- Triage burden: Findings require developer review and prioritization
Security Checklist
- Install Semgrep and run the default security rule set (p/security-audit)
- Add framework-specific rules (p/nextjs, p/react, p/django)
- Write custom rules for your project’s specific security patterns
- Integrate into CI/CD to scan every PR automatically
- Configure rules to match AI-generated code patterns
- Review and triage findings by severity
- Create team-specific rules for common AI code mistakes
- Use semgrep –autofix for automatically fixable issues
- Monitor the Semgrep registry for new relevant rules
- Combine with DAST and SCA for comprehensive security coverage
Frequently Asked Questions
Is Semgrep free?
Semgrep OSS (open-source engine) is completely free. Semgrep Cloud (managed platform with team features) has a free tier for small teams and paid plans for larger organizations. The community rule registry is free and contains thousands of rules.
Can I write custom rules for AI-generated code?
Yes, this is Semgrep’s strength. You can write rules like ‘flag any eval() call,’ ‘require parameterized queries in all database operations,’ or ‘detect hardcoded API keys matching specific patterns.’ Custom rules let you codify your team’s security standards and catch AI-specific anti-patterns.
How does Semgrep compare to ESLint security plugins?
Semgrep is language-agnostic with more powerful pattern matching. ESLint is JavaScript/TypeScript-specific but integrates deeper into the editing workflow. For full-stack projects, use both: ESLint for real-time JavaScript feedback and Semgrep for comprehensive cross-language security scanning in CI/CD.