CVE-2019-5418

Cybersecurity and Infrastructure Security Agency Known Exploited Vulnerabilities CVE-2019-5418

Rails Ruby on Rails contains a path traversal 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.

Open Source Vulnerabilities GHSA-86g5-2wh3-gc9j

# 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: ``` ruby 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: ``` ruby 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: ``` ruby $ 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 <[email protected]> of GitHub

Open Source Vulnerabilities CVE-2019-5418

There is a File Content Disclosure vulnerability in Action View <5.2.2.1, <5.1.6.2, <5.0.7.2, <4.2.11.1 and v3 where specially crafted accept headers can cause contents of arbitrary files on the target system's filesystem to be exposed.