In a previous blog post, I outlined some ModSecurity defenses to help protect Ruby on Rails users from the XML parsing vulnerabilities. Hopefully you have had a chance to update RoR for your site. If not, you might want to stop what you are doing and fix it now... We identified a few attack probes on our WASC Distributed Web Honeypot Project sensors recently looking for this vuln.
Here are some screenshots taken from our central
host that is using the ModSecurity Audit log data:
Initial String Testing:
The attacker is sending a sample testing string value of "hello".
Testing for YAML parsing vulnerabilities 1:
Attacker then sends the YAML payload with some ruby exploit code however the object is incomplete.
Testing for YAML parsing vulnerabilities 2:
In this final payload, the attacker sends the YAML payload with the ruby code to execute the local time.
Nmap NSE Script
A quick search for those attack payloads turned up a new Nmap NSE script on GitHub called http-rails-xml-parser.nse:
So we have our tool identified. This script doesn't exploit the vulnerabilty but does identify vulnerable hosts. Bottom line is that scripts/tools are out there now and actively scanning the web-o-sphere for vulnerable sites. Better patch/upgrade ASAP....