ruby.lang.security.dangerous-subshell.dangerous-subshell

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Detected non-static command inside .... If unverified user data can reach this call site, this is a code injection vulnerability. A malicious actor can inject a malicious script to execute arbitrary code.

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Defintion

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rules:
  - id: dangerous-subshell
    patterns:
      - pattern: |
          `...#{$VAL}...`
      - pattern-not: |
          `...#{"..."}...`
      - pattern-not-inside: |
          $VAL = "..."
          ...
    message: Detected non-static command inside `...`. If unverified user data can
      reach this call site, this is a code injection vulnerability. A malicious
      actor can inject a malicious script to execute arbitrary code.
    metadata:
      cwe:
        - "CWE-94: Improper Control of Generation of Code ('Code Injection')"
      owasp:
        - A03:2021 - Injection
      category: security
      technology:
        - ruby
      references:
        - https://owasp.org/Top10/A03_2021-Injection
      cwe2022-top25: true
      subcategory:
        - audit
      likelihood: LOW
      impact: HIGH
      confidence: LOW
      license: Commons Clause License Condition v1.0[LGPL-2.1-only]
      vulnerability_class:
        - Code Injection
    severity: WARNING
    languages:
      - ruby

Examples

dangerous-subshell.rb

def test_calls(user_input)
# ruleid: dangerous-subshell
  result = `foo #{user_input} bar`

# ruleid: dangerous-subshell
  result2 = %x{foo #{user_input} bar}

# ruleid: dangerous-subshell
  cmd = `foo #{user_input} bar #{smth_else}`

# ok: dangerous-subshell
  smth = `ls testdir`.split[1]

# ok: dangerous-subshell
  ok_cmd = `echo oops && exit 99`

  hardcode = "testdir"
# ok: dangerous-subshell
  ok_cmd2 = %{ls #{hardcode} -lah}

end