COMMON WEAKNESS ENUMERATIONIncomplete

CWE-1336

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.

Soyutlama

Base

Yapı

Simple

Sömürü İhtimali

Medium

Problemi anla

Problem nedir?

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.

Genişletilmiş açıklama

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.

Terminoloji

Alternatif adlar ve kullanım biçimleri

Server-Side Template Injection / SSTI

This term is used for injection into template engines being used by a server.

Client-Side Template Injection / CSTI

This term is used for injection into template engines being used by a client.

Kök neden

Problem nasıl ve ne zaman oluşur?

Yaşam döngüsü evresi

Architecture and Design

The developer might choose a template engine that makes it easier for programmers to write vulnerable code.

Yaşam döngüsü evresi

Implementation

The programmer might not use engine's built-in sandboxes or other capabilities to escape or otherwise prevent template injection from untrusted input.

Risk

Başarılı sömürü neye yol açar?

Execute Unauthorized Code or Commands

Etkilenen güvenlik alanları: Integrity

Savunma

Nasıl önlenir ve çözülür?

Architecture and Design

Mimari ve tasarım yaklaşımı

Detay
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.

Implementation

Uygulama aşaması savunması

Detay
Use the template engine's sandbox or restricted mode, if available.

Doğrulama

Nasıl tespit edilir?

Automated Static Analysis

High
Automated static analysis, commonly referred to as Static Application Security Testing (SAST), can find some instances of this weakness by analyzing source code (or binary/compiled code) without having to execute it. Typically, this is done by building a model of data flow and control flow, then searching for potentially-vulnerable patterns that connect "sources" (origins of input) with "sinks" (destinations where the data interacts with external components, a lower layer such as the OS, etc.)