The procedure to update the system OpenSSL package will depend on you Linux distribution:
apt-based systems: Ubuntu, Debian...
sudo apt-get update
sudo apt-get install -y libssl1.0.0 openssl
And then check that the version was updated (or patched, with a recent "built on" date):
/usr/bin/openssl version -a
OpenSSL 1.0.1 14 Mar 2012
built on: Mon Apr 7 20:33:29 UTC 2014
...
You will also need to restart any service using libssl. To check the list of those services, you could use the below command:
sudo lsof -n | grep ssl | grep DEL
vsftpd 479 root DEL REG 202,1 394910 /lib/x86_64-linux-gnu/libssl.so.1.0.0
monit 1254 root DEL REG 202,1 394910 /lib/x86_64-linux-gnu/libssl.so.1.0.0
And then restart the services (depending on your specific system):
sudo /etc/init.d/monit restart
sudo /etc/init.d/vsftpd restart
yum-base systems: RedHat, CentOS, Fedora...
sudo yum -y update openssl
And then check that the version was updated (or patched, with a recent "built on" date):
/usr/bin/openssl version -a
OpenSSL 1.0.1 14 Mar 2012
built on: Mon Apr 7 20:33:29 UTC 2014
...
You will also need to restart any service using libssl. To check the list of those services, you could use the below command:
sudo lsof -n | grep ssl | grep DEL
vsftpd 479 root DEL REG 202,1 394910 /lib/x86_64-linux-gnu/libssl.so.1.0.0
monit 1254 root DEL REG 202,1 394910 /lib/x86_64-linux-gnu/libssl.so.1.0.0
And then restart the services (depending on your specific system):
sudo /etc/init.d/monit restart
sudo /etc/init.d/vsftpd restart
Next Steps
First, after apllying the patches above, double-check whether your web site is ok now using this tool:
The vulnerability allows an attacker to steal you private keys, which would allow it to decrypt any information, as well as impersonating your server so it is advised to revoke the compromised keys and reissuing and redistributing new ones.
This is only necessary if you already configured HTTPS with your own certificate. In this case regenerate new certificates and configure them again in your server.