As far as I know there's no buffer exploits publicly available for Tor servers. If there were, the Tor team would patch it very quickly. Running a firewall wouldn't hurt, just make sure you aren't interfering with the traffic coming into or out of the Tor network.
Ringo William Adams wrote: > I incorrectly posted the following to your blog. > > Please ignore the blog post. > > * > * > > *Greetings:* > > *I gather when running as a relay server, there is a publicly exposed > listener. > Is it vulnerable to a buffer exploit? > if so, what kind of protective firewalling does it need in order for the > server > machine to host it safely?* > > *Thanks,* > > *wlarip* >