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/formatsfilter.rb frozenstringliteral: 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

Directory traversal vulnerability in Action View in Ruby on Rails allows remote attackers to read arbitrary files.

Directory traversal vulnerability in actionpack/lib/abstractcontroller/base.rb in the implicit-render implementation in Ruby on Rails before 3.2.18, 4.0.x before 4.0.5, and 4.1.x before 4.1.1, when certain route globbing configurations are enabled, allows remote attackers to read arbitrary files via a crafted request.

There is a potential denial of service vulnerability in MODULE / COMPONENT. This vulnerability has been assigned the CVE identifier CVE-2019-5419.

Versions Affected: All. Not affected: None. Fixed Versions: 6.0.0.beta3, 5.2.2.1, 5.1.6.2, 5.0.7.2, 4.2.11.1

Impact ------ Specially crafted accept headers can cause the Action View template location code to consume 100% CPU, causing the server unable to process requests. This impacts all Rails applications that render views.

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 wrapping render calls with respondto blocks. For example, the following example is vulnerable:

class UserController < ApplicationController def index render "index" end end

But the following code is not vulnerable:

class UserController < ApplicationController def index respondto |format| format.html { render "index" } end end end

Implicit rendering is impacted, so this code is vulnerable:

class UserController < ApplicationController def index end end

But can be changed this this:

class UserController < ApplicationController def index respondto |format| format.html { render "index" } end end end

Alternatively to specifying the format, the following monkey patch can be applied in an initializer:

$ cat config/initializers/formatsfilter.rb frozenstringliteral: true

ActionDispatch::Request.prepend(Module.new do def formats super().select do |format| format.symbol || format.ref == "/" end end end)

Patches ------- To aid users who aren't able to upgrade immediately we have provided patches for the two supported release series. They are in git-am format and consist of a single changeset.

6-0-action-view-dos.patch - Patch for 6.0 series 5-2-action-view-dos.patch - Patch for 5.2 series 5-1-action-view-dos.patch - Patch for 5.1 series 5-0-action-view-dos.patch - Patch for 5.0 series 4-2-action-view-dos.patch - Patch for 4.2 series

Please note that only the 5.2.x, 5.1.x, 5.0.x, and 4.2.x series are supported at present. Users of earlier unsupported releases are advised to upgrade as soon as possible as we cannot guarantee the continued availability of security fixes for unsupported releases.

Also note that the patches for this vulnerability are the same as CVE-2019-5418.

Credits ------- Thanks to John Hawthorn <john@hawthorn.email> of GitHub

-- Aaron Patterson http://tenderlovemaking.com/