Overview
Injection vulnerabilities in Flask can lead to unauthorized data access, data tampering, and in some cases remote code execution when untrusted input is processed by the application. Real-world impact includes exfiltration of user data, bypassed authentication checks, and unintended server-side actions if attackers can influence SQL queries or template rendering. While no CVEs are provided in this guide, the risks described reflect common patterns seen in Flask apps that interpolate user input into SQL or render user-provided templates. Understanding these patterns helps teams recognize at-risk code and implement robust mitigations across versions and deployments.
Code Fix Example
Flask API Security Remediation
Vulnerable SQL pattern:\ncursor.execute("SELECT id, username FROM users WHERE username = '%s'" % username)\n\nFix:\ncursor.execute("SELECT id, username FROM users WHERE username = ?", (username,))\n\nVulnerable Template pattern:\ntemplate = request.args.get("template", "")\nreturn render_template_string(template)\n\nFixed Template pattern:\nreturn render_template_string("Hello {{ name }}!", name=request.args.get("name", ""))