[CVE-2016-2098] Possible remote code execution vulnerability in Action Pack

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Rafael Mendonça França

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Feb 29, 2016, 2:31:53 PM2/29/16
to rubyonrail...@googlegroups.com, secu...@suse.de, oss-se...@lists.openwall.com, ruby-sec...@googlegroups.com
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:

```ruby
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:

```ruby
def show
  render params[:id]
end
```

To this:

```ruby
def show
  render verify_id(params[:id])
end

private
def verify_id(id)
  # 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!
4-2-secure_inline_with_params.patch
3-2-secure_inline_with_params.patch
4-1-secure_inline_with_params.patch
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