The Single Sign On Client (ubuntu-sso-client) for Ubuntu 11.04 and 11.10 does not properly validate SSL certificates when using HTTPS, which allows remote attackers to spoof a server and modify or read sensitive data via a man-in-the-middle (MITM) attack.
https://exchange.xforce.ibmcloud.com/vulnerabilities/76112
http://www.ubuntu.com/usn/USN-1464-1
http://www.securityfocus.com/bid/53829