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 john@hawthorn.email of GitHub
References
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
rendercalls withrespond_toblocks. For example, the following example is vulnerable:But the following code is not vulnerable:
Implicit rendering is impacted, so this code is vulnerable:
But can be changed this this:
Alternatively to specifying the format, the following monkey patch can be applied in an initializer:
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
References