Name: Thymeleaf Scanner

Thymeleaf is a popular Java-based templating engine used in various web applications to create dynamic web pages with rich UI features. Commonly used by developers to integrate backend data into a frontend HTML layout, Thymeleaf is extensively used in Spring and Spring Boot applications. It supports both HTML5 and modern web architecture, making it a preferred choice for web applications. Thymeleaf is often preferred for its ability to work both in web applications and standalone environments. It effectively integrates with Spring applications, providing an option for server-side rendering. It also facilitates natural templating to build layouts and complex views with embedded logic.

Server-Side Template Injection (SSTI) is a critical vulnerability that can be exploited in web applications when user input is embedded into templates without appropriate sanitization. Attackers may exploit SSTI in Thymeleaf to manipulate server-side templates, leading to unauthorized actions on the server. This vulnerability can be triggered when user data is dynamically included in a Thymeleaf template using expressions. Malicious actors use SSTI to execute arbitrary code or access sensitive server-side information. The impact of SSTI can be severe, often leading to full server compromise if exploited successfully. Proper input validation and sanitization are essential for protecting applications from SSTI.

The vulnerability in Thymeleaf arises from improper sanitization of user-supplied inputs embedded into templates. Attackers exploit SSTI by using crafted payloads that utilize dynamic expressions to achieve remote code execution. In this case, user inputs are injected into Thymeleaf templates using expression language features, often without validation checks. Endpoint parameters vulnerable to SSTI are usually those that accept user-generated data directly without filtering. Fuzzing methods are used to identify such inputs where SSTI is possible, with payloads attempting out-of-band interactions to confirm execution. Successful detection depends on the ability to interact with the server using resolved address and DNS request.

Exploitation of the SSTI vulnerability in Thymeleaf can wreak significant havoc, potentially leading to full server control. Once an attacker triggers SSTI, they can execute arbitrary commands on the server, achieving remote code execution capabilities. This may lead to unauthorized access to sensitive data, database manipulation, or backdoor installation for persistent access. Compromised servers could be further exploited to launch attacks on other systems within the network. Moreover, the presence of SSTI can undermine user trust and jeopardize compliance with security regulations. Detection and mitigation of this vulnerability are critical to maintaining system integrity and security.

REFERENCES

• https://www.acunetix.com/blog/web-security-zone/exploiting-ssti-in-thymeleaf/