Day 27 of 30 Day — 30 Vulnerabilities | Server-Side Template Injection (SSTI)

Day 27: Mastering Server-Side Template Injection (SSTI) — Essential Tricks & Techniques Based on Personal Experience and Valuable POCs

[ In collaboration with Abhijeet Kumawat ( LinkedIn | Twitter)]

Hey geeks, it4chis3c (Twitter) here with one more write-up on tricks & tips to detect SSTI. Today’s focus is on Server-Side Template Injection (SSTI) — a powerful and often overlooked vulnerability that can lead to severe security breaches. Let’s break down the essentials.

1. Brief Description

What is Server-Side Template Injection (SSTI)?

Server-Side Template Injection (SSTI) is a vulnerability that occurs when user input is unsafely incorporated into server-side templates. By exploiting this flaw, an attacker can execute arbitrary code on the server, leading to unauthorized access, data theft, or full system compromise.

How Does It Work?

SSTI typically arises when an application uses templating engines (like Jinja2, Thymeleaf, or Velocity) that render templates on the server-side. If user input is inserted into templates without proper validation or sanitization, an attacker can inject malicious code or expressions that the template engine will execute.