Template Injection (SSTI)

Summary

Server-Side Template Injection (SSTI) is a vulnerability that occurs when user input is improperly sanitized and embedded within a server-side template, allowing attackers to inject and execute arbitrary code on the server. This can lead to data theft, remote code execution, and full system compromise.

Key Characteristics

• Exploitation involves injecting malicious payloads into template engines used on the server side.
• Targets web applications that dynamically generate content using templates.
• Can lead to remote code execution, data leakage, and privilege escalation.
• Common in applications using popular template engines like Jinja2, Twig, or Velocity.
• Often results from insufficient input validation and improper handling of user-supplied data.

Defensive Controls

• Implement strict input validation and sanitization to prevent malicious template code.
• Use secure coding practices and avoid directly embedding user input into templates.
• Employ template engines with built-in sandboxing features to restrict code execution.
• Regularly update and patch template engines and related software components.
• Conduct security testing, including static analysis and penetration testing, to identify SSTI vulnerabilities.

Related Security Solutions

Web Application Firewalls (WAFs) can help detect and block SSTI attack payloads. Runtime Application Self-Protection (RASP) tools monitor application behavior to prevent exploitation. Secure coding frameworks and static application security testing (SAST) tools assist developers in identifying and mitigating injection flaws during development.