Injection

Injection Security Check (A05:2025)

What this checks

Protects against SQL, command, and template injection caused by passing user-controlled data to an interpreter without sanitization. Exploitation leads to full database read/write, remote code execution, and data exfiltration. For NoSQL-specific injection (MongoDB operator injection, $where), see nosql-injection.

Vulnerable patterns

• "SELECT * FROM users WHERE id = " + userId — user input concatenated into SQL
• exec("convert " + filename) — shell expansion allows ; rm -rf /
• eval(userInput) — arbitrary code execution from user-supplied string
• Template("Hello " + name) — template body built from user input

Fix immediately

For each vulnerable call site, apply the appropriate control:

• SQL: use parameterized queries or an ORM — never concatenate user input into query strings
• Shell: pass arguments as an array/list, never as an interpolated string — disable shell expansion
• Templates: use an engine that autoescapes by default and pass user values through the parameter interface. Python: Environment(autoescape=True) (bool literal, not select_autoescape() with from_string()). Go: html/template, never text/template for HTTP output. Java FreeMarker: cfg.setOutputFormat(HTMLOutputFormat.INSTANCE). Rust: handlebars (escapes by default). Never build the template body from user input.
• eval/exec: remove entirely — there is no safe way to evaluate user-supplied code strings

Flag the vulnerable call site, explain the risk and the correct fix pattern, then continue with the original task.

Verification

Confirm the following properties hold (language-agnostic):

• User-controlled values reach SQL only as bound parameters — never via string interpolation, concatenation, or format strings
• User-controlled values reach subprocess execution only as discrete argument list elements — never via a shell string or interpolated command string
• No dynamic evaluation of user-supplied strings as code (Python eval/exec, JS eval/new Function, etc. removed — not replaced with a safer-looking variant of the same function)
• Templates use an engine where HTML autoescaping is either enabled explicitly or is the documented default (Flask render_template, Go html/template, Rust handlebars, Jinja2 Environment(autoescape=True) — NOT Jinja2 Template() direct, NOT Go text/template), and user values are passed through the engine's parameter interface — never by building the template body from user input

References

• CWE-89 (SQL Injection)
• CWE-78 (OS Command Injection)
• CWE-94 (Code Injection)
• OWASP A05:2025 Injection