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Security Advisories: MDE2OlNlY3VyaXR5QWR2aXNvcnlHSFNBLW02M2otd2g1dy1jMjUy

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:

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

But the following code is not vulnerable:

class UserController < ApplicationController 
  def index 
    respond_to |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 
    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 [email protected] of GitHub

Permalink: https://github.com/advisories/GHSA-m63j-wh5w-c252
JSON: https://advisories.ecosyste.ms/api/v1/advisories/MDE2OlNlY3VyaXR5QWR2aXNvcnlHSFNBLW02M2otd2g1dy1jMjUy
Source: GitHub Advisory Database
Origin: Unspecified
Severity: High
Classification: General
Published: about 5 years ago
Updated: 6 months ago

CVSS Score: 7.5
CVSS vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Identifiers: GHSA-m63j-wh5w-c252, CVE-2019-5419
References:

Repository: https://github.com/rails/rails
Blast Radius: 43.3

Affected Packages

rubygems:actionview

Dependent packages: 354
Dependent repositories: 601,072
Downloads: 475,633,483 total
Affected Version Ranges: >= 6.0.0.beta1, < 6.0.0.beta3, >= 5.2.0, <= 5.2.2.0, >= 4.0.0, <= 4.2.11.0, >= 5.0.0, <= 5.0.7.1, >= 5.1.0, <= 5.1.6.1
Fixed in: 6.0.0.beta3, 5.2.2.1, 4.2.11.1, 5.0.7.2, 5.1.6.2
All affected versions: 4.1.0, 4.1.1, 4.1.2, 4.1.3, 4.1.4, 4.1.5, 4.1.6, 4.1.7, 4.1.8, 4.1.9, 4.1.10, 4.1.11, 4.1.12, 4.1.13, 4.1.14, 4.1.15, 4.1.16, 4.2.0, 4.2.1, 4.2.1-0.rc1, 4.2.2, 4.2.3, 4.2.4, 4.2.5, 4.2.6, 4.2.7, 4.2.8, 4.2.9, 4.2.10, 4.2.11, 5.0.0, 5.0.1, 5.0.2, 5.0.3, 5.0.4, 5.0.5, 5.0.6, 5.0.7, 5.1.0, 5.1.1, 5.1.2, 5.1.3, 5.1.4, 5.1.5, 5.1.6, 5.1.7, 5.2.0, 5.2.1, 5.2.2, 5.2.3, 5.2.4, 5.2.5, 5.2.6, 5.2.7, 5.2.8, 6.0.0, 6.0.1, 6.0.2, 6.0.3, 6.0.4, 6.0.5, 6.0.6, 6.1.0, 6.1.1, 6.1.2, 6.1.3, 6.1.4, 6.1.5, 6.1.6, 6.1.7, 7.0.0, 7.0.1, 7.0.2, 7.0.3, 7.0.4, 7.0.5, 7.0.6, 7.0.7, 7.0.8, 7.1.0, 7.1.1, 7.1.2, 7.1.3
All unaffected versions: