The version of sinatra in SCL, v1.3.2, seems to have a pretty bad bug in it: https://github.com/sinatra/sinatra/issues/452 This impacts Foreman which uses ruby SCL, but this bug would impact other apps too. The rack-protection gem would also need to be updated since versions of sinatra after 1.3.2 pull in newer versions, e.g 1.5.0
Don't think it is right time for Rebase, especially it would need rebase to Sinatra 1.4.x. I would much prefer just backport of the fix (seems to be straight forward, although I have not tried it yet).
Since the problem described in this bug report should be resolved in a recent advisory, it has been closed with a resolution of ERRATA. For information on the advisory, and where to find the updated files, follow the link below. If the solution does not work for you, open a new bug report. http://rhn.redhat.com/errata/RHEA-2013-1249.html