Server-Side Template Injection (SSTI) Pattern Regex for PHP

What this pattern does

This page provides a comprehensive, battle-tested regular expression for matching server-side template injection (ssti) pattern, ported and verified for PHP. In security-sensitive code, using an unverified regex can open the door to both false positives and denial-of-service attacks. The snippet below is ready to drop into your PHP project — whether you're validating in a Laravel validator, a WordPress plugin, or a standalone PHP script.

Php Implementation

<?php
// Server-Side Template Injection (SSTI) Pattern
// ReDoS-safe | RegexVault — Security > Injection Patterns

define('SERVERSIDE_TEMPLATE_INJECTION_SSTI_PATTERN_PATTERN', '/(?:\{\{[^}]*\}\}|\{%[^%]*%\}|\$\{[^}]*\}|#\{[^}]*\}|<#[^>]*>|@\{[^}]*\}|\[\[.*?\]\]|\{#[^}]*#\}|\{\{7\*7\}\}|\{\{config\}\}|\{\{self\}\}|__class__|__mro__|__import__)/');

function validate_serverside_template_injection_ssti_pattern(string $input): bool {
    return (bool) preg_match(SERVERSIDE_TEMPLATE_INJECTION_SSTI_PATTERN_PATTERN, $input);
}

// Example
var_dump(validate_serverside_template_injection_ssti_pattern("{{7*7}}")); // bool(true)

Test Cases

When to use this pattern

This pattern is drawn from the Security > Injection Patterns category and carries a ReDoS-safe certification. That matters for PHP developers because especially relevant in PHP where PCRE backtracking limits can trigger silent failures on malicious input. RegexVault audits patterns against known backtracking attack vectors, ensuring you have the necessary context before using this regex in a high-stakes production environment.

Common Pitfalls

Technical Notes

Template engines: Jinja2/Twig/Nunjucks use {{ }}, {% %}, Freemarker uses ${}, Ruby ERB uses <%=%>. The probe {{7*7}} (expected result 49) is the canonical SSTI detection test. __class__ and __mro__ are Python object introspection used in Jinja2 sandbox escapes.