bstrain74,
Alright, I spent a little more time on this one trying to find a match on the exact vulnerability and there is not a security advisory for this specific issue. There is however one for the Heartbleed vulnerability which the 5000 was reported immune to on 6.0 SP1 PR1 and earlier; this one is not likely as severe. I think the issue here would be, "The attacker would be required to intercept and alter network traffic, and do so in real time, to exploit the flaw; in that case, the attacker could potentially view and/or modify the otherwise secured traffic".
If you wanted to try shutting down the web server and test again I guess that is possible. Go to System > IP Settings > Web/SSH Settings and from there I am sure you can figure out if you want to shut just the web portion down or both it and SSH.
If that doesn't work for you then you can have your vendor put in a ticket with Mitel so they can give you a direct answer. I do know that we haven't moved to CentOS version 6 yet, but there is a patch update for version 5 that requires OpenSSL version 0.9.8e; according to the following, but I am not sure what version of OpenSSL we use.
For CentOS 5 you should have
openssl-0.9.8e-27.el5_10.3
openssl097a-0.9.7a-12.el5_10.1
Thanks,
TE