CWE-1336 Detail

CWE-1336

Improper Neutralization of Special Elements Used in a Template Engine
Incomplete
2021-07-20 00:00 +00:00
2024-07-16 00:00 +00:00

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Improper Neutralization of Special Elements Used in a Template Engine

The product uses a template engine to insert or process externally-influenced input, but it does not neutralize or incorrectly neutralizes special elements or syntax that can be interpreted as template expressions or other code directives when processed by the engine.

Extended Description

Many web applications use template engines that allow developers to insert externally-influenced values into free text or messages in order to generate a full web page, document, message, etc. Such engines include Twig, Jinja2, Pug, Java Server Pages, FreeMarker, Velocity, ColdFusion, Smarty, and many others - including PHP itself. Some CMS (Content Management Systems) also use templates.

Template engines often have their own custom command or expression language. If an attacker can influence input into a template before it is processed, then the attacker can invoke arbitrary expressions, i.e. perform injection attacks. For example, in some template languages, an attacker could inject the expression "{{7*7}}" and determine if the output returns "49" instead. The syntax varies depending on the language.

In some cases, XSS-style attacks can work, which can obscure the root cause if the developer does not closely investigate the root cause of the error.

Template engines can be used on the server or client, so both "sides" could be affected by injection. The mechanisms of attack or the affected technologies might be different, but the mistake is fundamentally the same.

Informations

Modes Of Introduction

Architecture and Design : The developer might choose a template engine that makes it easier for programmers to write vulnerable code.
Implementation : The programmer might not use engine's built-in sandboxes or other capabilities to escape or otherwise prevent template injection from untrusted input.

Applicable Platforms

Language

Name: Java (Undetermined)
Name: PHP (Undetermined)
Name: Python (Undetermined)
Name: JavaScript (Undetermined)
Class: Interpreted (Undetermined)

Operating Systems

Class: Not OS-Specific (Undetermined)

Technologies

Name: AI/ML (Undetermined)
Class: Client Server (Undetermined)

Common Consequences

Scope Impact Likelihood
IntegrityExecute Unauthorized Code or Commands

Observed Examples

Reference Description
CVE-2024-34359Chain: Python bindings for LLM library do not use a sandboxed environment when parsing a template and constructing a prompt, allowing jinja2 Server Side Template Injection and code execution - one variant of a "prompt injection" attack.
CVE-2017-16783server-side template injection in content management server
CVE-2020-9437authentication / identity management product has client-side template injection
CVE-2020-12790Server-Side Template Injection using a Twig template
CVE-2021-21244devops platform allows SSTI
CVE-2020-4027bypass of Server-Side Template Injection protection mechanism with macros in Velocity templates
CVE-2020-26282web browser proxy server allows Java EL expressions from Server-Side Template Injection
CVE-2020-1961SSTI involving mail templates and JEXL expressions
CVE-2019-19999product does not use a "safe" setting for a FreeMarker configuration, allowing SSTI
CVE-2018-20465product allows read of sensitive database username/password variables using server-side template injection

Potential Mitigations

Phases : Architecture and Design
Choose a template engine that offers a sandbox or restricted mode, or at least limits the power of any available expressions, function calls, or commands.
Phases : Implementation
Use the template engine's sandbox or restricted mode, if available.

Vulnerability Mapping Notes

Rationale : This CWE entry is at the Base level of abstraction, which is a preferred level of abstraction for mapping to the root causes of vulnerabilities.
Comments : Carefully read both the name and description to ensure that this mapping is an appropriate fit. Do not try to 'force' a mapping to a lower-level Base/Variant simply to comply with this preferred level of abstraction.

Notes

Since expression languages are often used in templating languages, there may be some overlap with CWE-917 (Expression Language Injection). XSS (CWE-79) is also co-located with template injection.
The interrelationships and differences between CWE-917 and CWE-1336 need to be further clarified.

References

REF-1193

Server-Side Template Injection
James Kettle.
https://portswigger.net/research/server-side-template-injection

REF-1194

Server-Side Template Injection: RCE For The Modern Web App
James Kettle.
https://www.youtube.com/watch?v=3cT0uE7Y87s

Submission

Name Organization Date Date Release Version
CWE Content Team MITRE 2021-07-19 +00:00 2021-07-20 +00:00 4.5

Modifications

Name Organization Date Comment
CWE Content Team MITRE 2022-06-28 +00:00 updated Maintenance_Notes, Relationships
CWE Content Team MITRE 2023-04-27 +00:00 updated Relationships
CWE Content Team MITRE 2023-06-29 +00:00 updated Mapping_Notes
CWE Content Team MITRE 2024-07-16 +00:00 updated Applicable_Platforms, Observed_Examples
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