Patch immediately
In a word...OUCH!
http://metasploit.com/users/hdm/tools/debian-openssl/
In case you don't care to follow that link, it's a link to a tool that will generate all possible SSH keys based on the openssl PRNG used by debian
A recently released security announcement affects Debian and Debian-derived systems (Ubuntu, Knoppix, etc). The primary risk posed by this vulnerability is to SSH host keys, though SSL and OpenVPN keys are also at-risk.
We have seen a significant increase in scanning for vulnerable
systems, and several exploits are now publicly available.
Anyone running Debian or one of its derivatives is urged to patch and
regenerate SSH/SSL/VPN keys as necessary. For more information:
http://www.debian.org/security/2008/dsa-1576