Red Hat 6
The openssl versions openssl-1.0.1e-15 through openssl-1.0.1e-16.el6_5.4 had a significant bug called "heartbleed" CVE-2014-0160. The bug allows anyone with access to the server through the internet to read parts of memory. It was limited to 64kb at a time but can be repeated multiple times to gain confidential information even over a secure network since the bug is local to the server. Security keys, passwords, usernames, emails, and other confidential information could be leaked. While a hacker cannot request specific information it gets whatever is passing through RAM at that moment.