As just about every security-related publication has reported today, a critical vulnerability in OpenSSL has been discovered yesterday. OpenSSL is a cryptographic software library, which provides SSL/TSL encryption functionality for network traffic all over the Internet. It’s used by Apache and nginx web servers that serve well over half of the world’s web sites, it powers virtual private networks, instant messaging networks and even email. It’s also widely used in client software, devices and appliances.

Because of a bug in implementation of TLS Heartbeat extension, remote attackers are potentially able to trigger a memory leak on an affected server and obtain different kinds of sensitive information including server’s private keys. The most embarrassing part of this is that the bug has been discovered in past OpenSSL releases dating back to 2012. Specifically, all OpenSSL versions from 1.0.1 to 1.0.1f are vulnerable. The bug has been fixed in the version 1.0.1g, released yesterday.

Needless to say, potential consequences of this vulnerability are huge. Any remote attacker can theoretically leak a server’s private key and then easily decrypt any past or future SSL-encrypted traffic from that server without leaving any traces of an attack. This means that simply patching the vulnerability is not enough; all services involved in handling sensitive information also have to change their private keys and reissue their SSL certificates.

For more information, I recommend checking out and to see whether your server is compromised, use this test. You can also check the OpenSSL version installed on your server directly.

If your server is compromised, the first step should be updating OpenSSL to 1.0.1g – all major Linux and *BSD distributions have already made updates available. If it’s not possible, you can recompile OpenSSL from the source code with heartbeat support disabled.

Unfortunately, it’s not possible to detect whether your server has already been attacked using this bug. So, to be on the safe side, you should consider reissuing your SSL certificates with new private keys.

One rather sad consequence of the whole Heartbleed debacle is that it delivered a serious blow to a major claim of open source proponents that open source software is inherently more secure because more people can inspect its source code and find possible vulnerabilities. While potentially it is true, in reality not many people would do that for such a large-scale project like OpenSSL just out of curiosity. I can only hope that finally someone will have a good reason to sponsor a proper security audit for OpenSSL and other open source security software.

This is also a good opportunity for service providers to upgrade their SSL key length to ensure more reliable encryption.