A denial of service (DoS) vulnerability was found on the BigDecimal standard library of Ruby. Conversion from BigDecimal objects into Float numbers had a problem which enables attackers to effectively cause segmentation faults.

ActiveRecord relies on this method, so most Rails applications are affected by this. Though this is not a Rails-specific issue.

We’re currently  building new Ruby packages for Brightbox customers with the relevant patches to fix this vulnerability. We’ll keep this post updated with the latest news.

UPDATE, 15:46 BST: New Ruby EE packages are now available in our Ruby Enterprise Ubuntu repository. We’re working on updates for the standard Ubuntu version of Ruby.

You can confirm that the update fixes the bug with the following command:

ruby -e 'require "bigdecimal";BigDecimal("E99999999").to_s("F");puts "OK"'

If your version of Ruby is vulnerable, you’ll get a “Segmentation fault” error message, otherwise it prints “OK”.

UPDATE: Official Ubuntu packages to fix this vulnerability are now available.  The Hardy package is libruby1.8 version 1.8.6.111-2ubuntu1.3 and the Dapper package is libruby1.8 version 1.8.4-1ubuntu1.7.  The packages will be available for install after a normal apt-get update.

Details of the bugs have been kept officially secret but people are figuring it out for themselves (thanks to Zed in particular).  This secrecy has just contributed to the fear, uncertainty and doubt surrounding the issues and hasn’t helped the situation at all.

We currently recommend sitting tight until proper fixes are available.  When this happens, distros will release new packages in the usual manner.  Brightboxes are based on the Ubuntu distro and their security team are aware of the problem and are working on it (see the bug status here).

For those of you using the standard Ruby from Dapper (most of you) you should be able to just upgrade  using aptitude as soon as Ubuntu release new packages.  For those of you using the backported Ruby 1.8.6 packages, you’ll need to wait for us to backport the fixes once they’re released.  We’ll obviously be doing this asap.

We’ll update the blog as we know more.

UPDATE: Ubuntu have fixed ruby1.8 packages available now. They have already appeared in the Ubuntu security repository and are available for install.  Preliminary testing of the Dapper packages has been successful (gems with native libraries too).  We’re re-backporting the Hardy 1.8.6 packages right now and they’ll be available soon.

UPDATE: We have the fixed Hardy packages (1.8.6-p111) backported to Dapper available on the Brightbox testing apt repository.  They’ve passed a lot of preliminary tests but have not been tested extensively in production yet.  Please report any problems  with them (segfaults etc.) to support@brightbox.co.uk.