“uninitialized constant REXML::VERSION” with Rails 2.1.1 and Rails 2.2 10 Sep 08

We’ve found a minor problem with Rails 2.1.1 (and Rails 2.2) on our Brightboxes.

Because we use Ubuntu Dapper, which ships with Ruby 1.8.4, it includes an earlier version of the REXML library (for XML processing). As you may know, there was a recent security vulnerability to do with the REXML library and these latest two versions of Rails include a fix for this.

Unfortunately, the library that ships with 1.8.4 is slightly incorrect. Ruby conventions state that a constant should be all capitals so, quite rightly, the Rails updates check for a constant called REXML::VERSION. However, in 1.8.4, the constant is actually called REXML::Version meaning that Rails falls over with an “uninitialized constant REXML::VERSION” error.

The quick fix is to manually edit /usr/lib/ruby/1.8/rexml/rexml.rb and add a new (correctly named constant). You will need to use sudo to edit the file, as it is owned by root; after editing the file should look something like:

module REXML
        Copyright = "Copyright © 2001, 2002, 2003, 2004 Sean Russell <ser@germane-software.com>"
        Date = "2005/224"
        Version = "3.1.3"
        VERSION = "3.1.3"
end

We are also looking at our options for a permanent fix for this issue.