The Debian team has provided a tool that can be used to determine if any such weak keys exist on the system, and it can be run by anyone, regardless of whether they use Debian or not.
Read it here
A recent vulnerability was found in the OpenSSL package as provided by Debian and Debian-based Linux distributions, such as Ubuntu, that broke the effectiveness of the OpenSSL PRNG (Predictable Random Number Generator). This vulnerability caused OpenSSL to generate weak keys for anything relying on OpenSSL, including SSL certificates, OpenSSH keys, and OpenVPN keys. Any OpenSSL-based key generated on a Debian-based system since September 2006 by the openssl, ssh-keygen, or openvpn keygen commands are vulnerable to this issue.