In general, a standard system upgrade is sufficient to effect the
USN-612-3 addressed a weakness in OpenSSL certificate and key
generation and introduced openssl-blacklist to aid in detecting
vulnerable certificates and keys. This update adds RSA-4096
blacklists to the openssl-blacklist-extra package and adjusts
openssl-vulnkey to properly handle RSA-4096 and higher moduli.
Original advisory details:
A weakness has been discovered in the random number generator used
by OpenSSL on Debian and Ubuntu systems. As a result of this
weakness, certain encryption keys are much more common than they
should be, such that an attacker could guess the key through a
brute-force attack given minimal knowledge of the system. This
particularly affects the use of encryption keys in OpenSSH, OpenVPN
and SSL certificates.