resolv.rb in Ruby 1.8.5 and earlier, 1.8.6 before 1.8.6-p287, 1.8.7 before 1.8.7-p72, and 1.9 r18423 and earlier uses sequential transaction IDs and constant source ports for DNS requests, which makes it easier for remote attackers to spoof DNS responses, a different vulnerability than CVE-2008-1447.

More... (http://web.nvd.nist.gov/view/vuln/detail?vulnId=CVE-2008-3905)