The HTTP clients in the (1) httplib, (2) urllib, (3) urllib2, and (4) xmlrpclib libraries in CPython (aka Python) 2.x before 2.7.9 and 3.x before 3.4.3, when accessing an HTTPS URL, do not (a) check the certificate against a trust store or verify that the server hostname matches a domain name in the subject's (b) Common Name or (c) subjectAltName field of the X.509 certificate, which allows man-in-the-middle attackers to spoof SSL servers via an arbitrary valid certificate.
https://www.python.org/downloads/release/python-279/
https://support.apple.com/kb/HT205031
https://security.gentoo.org/glsa/201503-10
https://access.redhat.com/errata/RHSA-2017:1868
https://access.redhat.com/errata/RHSA-2017:1162
https://access.redhat.com/errata/RHSA-2016:1166
http://www.securityfocus.com/bid/71639
http://www.oracle.com/technetwork/topics/security/bulletinoct2015-2511968.html
http://www.oracle.com/technetwork/topics/security/bulletinjan2015-2370101.html
http://www.openwall.com/lists/oss-security/2014/12/11/1
http://lists.apple.com/archives/security-announce/2015/Aug/msg00001.html