Package Instance

Circumvention of file size limits in ActiveStorage
There is a vulnerability in ActiveStorage's S3 adapter that allows the Content-Length of a direct file upload to be modified by an end user.

Versions Affected:  rails < 5.2.4.2, rails < 6.0.3.1
Not affected:       Applications that do not use the direct upload functionality of the ActiveStorage S3 adapter.
Fixed Versions:     rails >= 5.2.4.3, rails >= 6.0.3.1

Impact
------

Utilizing this vulnerability, an attacker can control the Content-Length of an S3 direct upload URL without receiving a new signature from the server. This could be used to bypass controls in place on the server to limit upload size.

Workarounds
-----------

This is a low-severity security issue. As such, no workaround is necessarily until such time as the application can be upgraded.

Ability to forge per-form CSRF tokens in Rails
It is possible to, given a global CSRF token such as the one present in the authenticity_token meta tag, forge a per-form CSRF token for any action for that session.

Impact
------

Given the ability to extract the global CSRF token, an attacker would be able to construct a per-form CSRF token for that session.

Workarounds
-----------

This is a low-severity security issue. As such, no workaround is necessarily until such time as the application can be upgraded.

Possible Strong Parameters Bypass in ActionPack
There is a strong parameters bypass vector in ActionPack.

Versions Affected:  rails <= 6.0.3
Not affected:       rails < 5.0.0
Fixed Versions:     rails >= 5.2.4.3, rails >= 6.0.3.1

Impact
------
In some cases user supplied information can be inadvertently leaked from
Strong Parameters.  Specifically the return value of `each`, or `each_value`,
or `each_pair` will return the underlying "untrusted" hash of data that was
read from the parameters.  Applications that use this return value may be
inadvertently use untrusted user input.

Impacted code will look something like this:

```
def update
  # Attacker has included the parameter: `{ is_admin: true }`
  User.update(clean_up_params)
end

def clean_up_params
   params.each { |k, v|  SomeModel.check(v) if k == :name }
end
```

Note the mistaken use of `each` in the `clean_up_params` method in the above
example.

Workarounds
-----------
Do not use the return values of `each`, `each_value`, or `each_pair` in your
application.

Moderate severity vulnerability that affects rails
Cross-site scripting (XSS) vulnerability in the strip_tags function in Ruby on Rails before 2.2.s, and 2.3.x before 2.3.5, allows remote attackers to inject arbitrary web script or HTML via vectors involving non-printing ASCII characters, related to HTML::Tokenizer and actionpack/lib/action_controller/vendor/html-scanner/html/node.rb.

Path Traversal in Action View
# 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 <john@hawthorn.email> of GitHub

actionpack Improper Input Validation vulnerability
`actionpack/lib/action_view/lookup_context.rb` in Action View in Ruby on Rails 3.x before 3.2.16 and 4.x before 4.0.2 allows remote attackers to cause a denial of service (memory consumption) via a header containing an invalid MIME type that leads to excessive caching.

Rails Denial of Service vulnerability
Unspecified vulnerability in the "dependency resolution mechanism" in Ruby on Rails 1.1.0 through 1.1.5 allows remote attackers to execute arbitrary Ruby code via a URL that is not properly handled in the routing code, which leads to a denial of service (application hang) or "data loss," a different vulnerability than CVE-2006-4111.

# Denial of Service Vulnerability in Action View

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 `respond_to` blocks.  For example, the following example is vulnerable: 

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

But the following code is not vulnerable: 

```ruby 
class UserController < ApplicationController 
  def index 
    respond_to |format| 
      format.html { render "index" } 
    end 
  end 
end 
``` 

Implicit rendering is impacted, so this code is vulnerable: 

```ruby 
class UserController < ApplicationController 
  def index 
  end 
end 
``` 

But can be changed this this: 

```ruby 
class UserController < ApplicationController 
  def index 
    respond_to |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/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) 
``` 

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