File Content Disclosure in Action View
Impact
There is a possible file content disclosure vulnerability in Action View. Specially crafted accept headers in combination with calls to render file: can cause arbitrary files on the target server to be rendered, disclosing the file contents.
The impact is limited to calls to render which render file contents without a specified accept format. Impacted code in a controller looks something like this:
class UserController < ApplicationController
def index
render file: "#{Rails.root}/some/file"
end
end Rendering templates as opposed to files is not impacted by this vulnerability.
All users running an affected release should either upgrade or use one of the workarounds immediately.
Releases
The 6.0.0.beta3, 5.2.2.1, 5.1.6.2, 5.0.7.2, and 4.2.11.1 releases are available at the normal locations.
Workarounds
This vulnerability can be mitigated by specifying a format for file rendering, like this:
class UserController < ApplicationController
def index
render file: "#{Rails.root}/some/file", formats: [:html]
end
end In summary, impacted calls to render look like this:
render file: "#{Rails.root}/some/file"
The vulnerability can be mitigated by changing to this:
render file: "#{Rails.root}/some/file", formats: [:html]
Other calls to render are not impacted.
Alternatively, the following monkey patch can be applied in an initializer:
$ cat config/initializers/formats_filter.rb
# frozen_string_literal: true
ActionDispatch::Request.prepend(Module.new do
def formats
super().select do |format|
format.symbol || format.ref == "*/*"
end
end
end) Credits
Thanks to John Hawthorn john@hawthorn.email of GitHub
References
File Content Disclosure in Action View
Impact
There is a possible file content disclosure vulnerability in Action View. Specially crafted accept headers in combination with calls to
render file:can cause arbitrary files on the target server to be rendered, disclosing the file contents.The impact is limited to calls to
renderwhich render file contents without a specified accept format. Impacted code in a controller looks something like this:Rendering templates as opposed to files is not impacted by this vulnerability.
All users running an affected release should either upgrade or use one of the workarounds immediately.
Releases
The 6.0.0.beta3, 5.2.2.1, 5.1.6.2, 5.0.7.2, and 4.2.11.1 releases are available at the normal locations.
Workarounds
This vulnerability can be mitigated by specifying a format for file rendering, like this:
In summary, impacted calls to
renderlook like this:The vulnerability can be mitigated by changing to this:
Other calls to
renderare not impacted.Alternatively, the following monkey patch can be applied in an initializer:
Credits
Thanks to John Hawthorn john@hawthorn.email of GitHub
References