httplib2 0.7.2, 0.8, and earlier, after an initial connection is made, does not verify that the server hostname matches a domain name in the subject's Common Name (CN) or subjectAltName field of the X.509 certificate, which allows man-in-the-middle attackers to spoof SSL servers via an arbitrary valid certificate.
http://www.ubuntu.com/usn/USN-1948-1
http://www.securityfocus.com/bid/52179