Possible remote code execution vulnerability in Action Pack

There is a possible remote code execution vulnerability in Action Pack.
This vulnerability has been assigned the CVE identifier CVE-2016-2098.

Versions Affected: 3.2.x, 4.0.x, 4.1.x, 4.2.x
Not affected: 5.0+
Fixed Versions: 3.2.22.2, 4.1.14.2, 4.2.5.2

Impact

Applications that pass unverified user input to the render method in a
controller or a view may be vulnerable to a code injection.

Impacted code will look like this:

class TestController < ApplicationController
  def show
    render params[:id]
  end
end

An attacker could use the request parameters to coerce the above example
to execute arbitrary ruby code.

All users running an affected release should either upgrade or use one of
the workarounds immediately.

Releases

The FIXED releases are available at the normal locations.

Workarounds

A workaround to this issue is to not pass arbitrary user input to the render
method. Instead, verify that data before passing it to the render method.

For example, change this:

def index
  render params[:id]
end

To this:

def index
  render verify_template(params[:id])
end

private
def verify_template(name)
  # add verification logic particular to your application here
end

Patches

To aid users who aren’t able to upgrade immediately we have provided a
patch for it. It is in git-am format and consist of a single changeset.

• 3-2-secure_inline_with_params.patch - Patch for 3.2 series
• 4-1-secure_inline_with_params.patch - Patch for 4.1 series
• 4-2-secure_inline_with_params.patch - Patch for 4.2 series

Credits

Thanks to both Tobias Kraze from makandra and joernchen of Phenoelit for
reporting this!