Template Injection
Template Injection [T1221]
Last updated
Template Injection [T1221]
Last updated
Name: Template Injection
ID: T1221
Tactics:
Template Injection is recognized by the MITRE ATT&CK framework under the technique identifier T1221 within the tactic category Initial Access and Execution. It involves exploiting vulnerabilities in template engines or templating systems, which are commonly used to dynamically generate documents, web pages, or emails. Attackers exploit improper input validation in these template engines to inject malicious payloads, enabling them to execute arbitrary code, disclose sensitive information, or escalate privileges within the targeted environment.
Template Injection occurs when user-controlled input is unsafely embedded into a template engine without proper sanitization or validation. Template engines such as Jinja2, Twig, Freemarker, Velocity, Thymeleaf, Smarty, ERB, and others are widely used in web applications and content management systems (CMS) to render dynamic content. Attackers exploit the trust placed by developers in these engines by injecting malicious template syntax into user inputs.
Technical details include:
Server-Side Template Injection (SSTI):
Occurs when user input is directly passed to a template engine without proper filtering.
Attackers inject special syntax recognized by the template engine to execute arbitrary code or commands.
Commonly affected template engines include Jinja2 (Python), Freemarker (Java), Twig (PHP), Smarty (PHP), Velocity (Java), and ERB (Ruby).
Client-Side Template Injection (CSTI):
Less common, but occurs when client-side JavaScript templating libraries (e.g., AngularJS, Vue.js) unsafely embed user input into templates.
Exploitation can lead to Cross-Site Scripting (XSS) attacks.
Typical execution methods involve:
Injecting payloads such as {{7*7}} or ${7*7} to test for vulnerable template engines.
Escalating to more advanced payloads such as accessing sensitive system variables, executing operating system commands, or reading files from the server.
Leveraging known template injection payloads and bypass techniques available in exploitation frameworks and cheat sheets.
Real-world procedures commonly observed:
Attackers initially identify template injection points via reconnaissance and fuzzing.
Payloads often escalate from simple arithmetic checks to sophisticated code execution attempts.
Attackers may combine this technique with other vulnerabilities for lateral movement or privilege escalation.
Template Injection is commonly used in various attack scenarios and stages, including:
Initial Access:
Attackers exploit publicly exposed web applications or CMS systems vulnerable to template injection to gain initial foothold.
Malicious actors target web forms, user-input fields, email template rendering, and dynamic content generation functions.
Execution:
Attackers leverage template injection vulnerabilities to execute arbitrary commands or scripts on the server.
Commonly used to run reverse shells, download further payloads, or perform system reconnaissance.
Privilege Escalation:
Attackers exploit template injection vulnerabilities that run under privileged accounts or contexts to escalate privileges on compromised systems.
Data Exfiltration:
Attackers use template injection vulnerabilities to read sensitive files, environment variables, or configuration data from the server.
Persistence:
Attackers may inject malicious templates or backdoors into CMS or templating systems to maintain persistent access.
Detection methods and tools commonly used to identify template injection include:
Input Validation and Monitoring:
Implementing strict input validation and sanitization routines.
Monitoring for unusual or suspicious template syntax in user inputs.
Web Application Firewalls (WAF):
Configuring WAF rules to detect and block known template injection payloads and patterns.
Analyzing HTTP traffic for suspicious template engine syntax ({{, ${, {%, etc.).
Application Security Testing Tools:
Static Application Security Testing (SAST) tools to detect insecure coding practices.
Dynamic Application Security Testing (DAST) tools to identify injection vulnerabilities during runtime.
Security Information and Event Management (SIEM):
Correlating logs and events from web servers and application frameworks.
Alerting on anomalies or unusual template engine errors and exceptions.
Indicators of Compromise (IoCs):
Unusual log entries showing template syntax errors or unexpected template parsing failures.
HTTP requests containing suspicious template engine syntax ({{7*7}}, ${7*7}, <div data-gb-custom-block data-tag="include" data-0='filename'></div>, etc.).
Server-side logs indicating attempts to access sensitive files or system variables via template engines.
Early detection of template injection vulnerabilities is crucial due to the significant impacts this technique can cause, such as:
Code Execution and Compromise:
Attackers can execute arbitrary commands, scripts, or code on vulnerable systems, leading to full compromise.
Privilege Escalation:
Exploitation may allow attackers to escalate their privileges, gaining administrative or root-level access.
Sensitive Data Exposure:
Attackers may access confidential files, configuration data, credentials, or environment variables stored on the compromised server.
Persistence and Long-Term Access:
Attackers can implant persistent backdoors or malicious templates within CMS or templating systems.
Reputation and Compliance Risks:
Organizations face potential regulatory fines, reputational damage, and loss of customer trust due to successful exploitation.
Operational Disruption:
Exploitation may lead to system downtime, data corruption, or unauthorized modifications affecting business operations.
Real-world examples highlighting template injection attacks, tools used, and impacts include:
Uber Bug Bounty SSTI (2016):
Security researcher identified a Jinja2 template injection vulnerability in Uber's internal web application.
Payloads injected allowed execution of arbitrary Python code, enabling access to internal data and systems.
Impact: Potential full internal network compromise; Uber rewarded the researcher through their bug bounty program.
Shopify SSTI Vulnerability (2019):
Researcher discovered a template injection vulnerability within Shopify's internal employee management system.
Exploited Freemarker template engine to achieve remote code execution and access sensitive internal data.
Impact: Potential exposure of sensitive employee and customer data; Shopify patched the vulnerability promptly.
Apache Struts OGNL Template Injection (CVE-2017-5638):
Attackers exploited an OGNL expression injection vulnerability in Apache Struts to execute arbitrary commands.
Notable incident: Equifax data breach, where attackers exploited this vulnerability to exfiltrate sensitive personal data of approximately 147 million people.
Impact: Massive data breach, significant financial losses, regulatory penalties, and reputational damage.
Tools and Frameworks Used:
Burp Suite (Intruder, Scanner) for fuzzing and detecting injection points.
Tplmap: Automated open-source tool designed specifically for detecting and exploiting template injection vulnerabilities.
Custom payload generators and cheat sheets publicly available for various template engines (e.g., PayloadAllTheThings repository).
Typical Attack Scenario:
Attacker identifies a vulnerable input field via reconnaissance and fuzzing.
Injects a simple payload ({{7*7}}) to confirm vulnerability presence.
Escalates payload complexity to execute arbitrary commands or read sensitive files.
Gains remote code execution, exfiltrates sensitive data, and establishes persistent access.
These examples illustrate the severity, frequency, and real-world implications of template injection vulnerabilities, underscoring the importance of proactive detection, prevention, and mitigation strategies.