[CVE-2016-0751] Possible Object Leak and Denial of Service attack in Action Pack

[Aaron Patterson]

Possible Object Leak and Denial of Service attack in Action Pack

There is a possible object leak which can lead to a denial of service
vulnerability in Action Pack. This vulnerability has been
assigned the CVE identifier CVE-2016-0751.

Versions Affected: All.
Not affected: None.
Fixed Versions: 5.0.0.beta1.1, 4.2.5.1, 4.1.14.1, 3.2.22.1

Impact
------
A carefully crafted accept header can cause a global cache of mime types to
grow indefinitely which can lead to a possible denial of service attack in
Action Pack.

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
-----------
This attack can be mitigated by a proxy that only allows known mime types in
the Accept header.

Placing the following code in an initializer will also mitigate the issue:

```ruby
require 'action_dispatch/http/mime_type'

Mime.const_set :LOOKUP, Hash.new { |h,k|
Mime::Type.new(k) unless k.blank?
}
```

Patches
-------
To aid users who aren't able to upgrade immediately we have provided patches for
the two supported release series. They are in git-am format and consist of a
single changeset.

* 5-0-mime_types_leak.patch - Patch for 5.0 series
* 4-2-mime_types_leak.patch - Patch for 4.2 series
* 4-1-mime_types_leak.patch - Patch for 4.1 series
* 3-2-mime_types_leak.patch - Patch for 3.2 series

Please note that only the 4.1.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.

Credits
-------
Aaron Patterson <3<3


--
Aaron Patterson
http://tenderlovemaking.com/