OpenSSH before 2.9.9, while using keypairs and multiple keys of different types in the ~/.ssh/authorized_keys2 file, may not properly handle the "from" option associated with a key, which could allow remote attackers to login from unauthorized IP addresses.
http://marc.info/?l=bugtraq&m=100154541809940&w=2
http://rhn.redhat.com/errata/RHSA-2001-114.html
https://exchange.xforce.ibmcloud.com/vulnerabilities/7179