Aaron Patterson (tenderlove) reports:
Serialized Attributes YAML Vulnerability with Rails 2.3 and 3.0
There is a vulnerability in the serialized attribute handling code in Ruby on
Rails 2.3 and 3.0, applications which allow users to directly assign to the
serialized fields in their models are at risk of Denial of Service or Remote
Code Execution vulnerabilities. This vulnerability has been assigned the CVE
Versions Affected: 2.3.x, 3.0.x and all earlier versions
Not affected: 3.1.0 and Above
Fixed Versions: None
The +serialize+ helper in Active Record allows developers to store various
objects serialized to a BLOB column in the database. The objects are
serialized and deserialized using YAML. If developers allow their users to
directly provide values for this attribute, an attacker could use a specially
crafted request to cause the application to deserialize arbitrary YAML.
Vulnerable applications will have models similar to this:
class Post < ActiveRecord::Base
and will allow foreign input to be directly assigned to the serialized column
post = Post.new
post.tags = params[:tags]
All users running an affected release should either apply one of the patches
or use one of the work arounds immediately.
In accordance with our maintenance policy, there will be no new releases of
Ruby on Rails 2.3 or 3.0 to address this vulnerability. The patches included
below have been pushed to the relevant branches in git.
To work around this issue, you must ensure that users cannot assign directly
to the serialized column. For example if you have a model Post which
serializes an array of tags you should use attr_accessible to prevent
attackers from changing these values directly:
class Post < ActiveRecord::Base
# because :tags isn't included in the accessible list, it will be protected from assignment by attackers.
attr_accessible :title, :content
Note: There are additional security concerns caused by allowing your users to
directly provide values for a serialized attribute like this. You should
consider making this change even if you apply the patches.
To aid users who are still running 2.3 or 3.0, we have included patches
against this vulnerability. They are in git-am format and consist of a
* 2-3-serialize.patch - Patch for 2.3 series
* 3-0-serialize.patch - Patch for 3.0 series
Please note that only the 3.1.x and 3.2.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.
Thanks to Tobias Kraze for reporting this issue to us and working with us on
Created attachment 696264 [details]
Created attachment 696265 [details]
Could you please create tracking bug for Fedora? Thank you.
rubygem-activerecord-3.0.11-6.fc17 has been pushed to the Fedora 17 stable repository. If problems still persist, please make note of it in this bug report.
Created rubygem-activesupport tracking bugs for this issue
Affects: fedora-all [bug 949207]
(In reply to comment #7)
> Could you please create tracking bug for Fedora? Thank you.
Apologies, next time can you mark this as needinfo? Created tracking bug #949207
Comment removed due to typo.
Red Hat would like to thank the Ruby on Rails project for reporting this issue. The Ruby on Rails project acknowledges Tobias Kraze as the original reporter.