Setroubleshood eats a lot of memory causing OOM. Attacker is able to perform a lot of HTTP requests with permission denied messages by SELinux and running setroubleshootd daemon will eats all available memory (2GB RAM + 4GB in swap in my case).
This problem should be addressed by the new setroubleshoot 2.0 series scheduled for inclusion in the RHEL 5.2 update.