Applying SAST to Any Application (Without Sonar, Snyk, Semgrep, or Veracode)

Most "how to add SAST to your pipeline" articles gravitate toward the same four names: SonarQube, Snyk, Semgrep, Veracode. They're solid tools, but they're not the only options, and sometimes you can't use them — budget constraints, air-gapped environments, licensing restrictions, or simply wanting something lightweight that lives entirely in your repo. The OWASP Source Code Analysis Tools page lists dozens of alternatives across every language. In this article I'll walk through applying Bandit , a free, open-source SAST tool for Python, to a real sample application — from finding vulnerabilities locally to wiring it into a CI/CD pipeline with GitHub Actions. The same workflow (install → configure → scan → fail the build on high-severity findings → track results over time) applies almost identically if you swap Bandit for other OWASP-listed tools like Brakeman (Ruby), FindSecBugs (Java), Gosec (Go), or Horusec (multi-language). Why Bandit? 100% open source (Apache 2.0), maintained under the PyCQA org. No account, no server, no license key — it runs as a CLI or a library. Understands Python's AST, so it catches real logic patterns, not just regex matches. Easy to tune with a config file and inline # nosec suppressions. ## 1. The sample application Let's use a small Flask app with a few intentionally introduced vulnerabilities — the kind of thing that slips into real codebases under deadline pressure. # app.py import subprocess import sqlite3 import pickle import yaml from flask import Flask , request app = Flask ( __name__ ) DB_PATH = " users.db " @app.route ( " /ping " ) def ping (): host = request . args . get ( " host " ) # Vulnerable: command injection via shell=True result = subprocess . run ( f " ping -c 1 { host } " , shell = True , capture_output = True ) return result . stdout @app.route ( " /user " ) def get_user (): user_id = request . args . get ( " id " ) conn = sqlite3 . connect ( DB_PATH ) cursor = conn . cursor () # Vulnerable: SQL injection via strin