curl and libcurl 7.27.0 through 7.35.0, when using the SecureTransport/Darwinssl backend, as used in in Apple OS X 10.9.x before 10.9.2, 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 when accessing a URL that uses a numerical IP address, which allows man-in-the-middle attackers to spoof servers via an arbitrary valid certificate.
http://www.getchef.com/blog/2014/04/09/enterprise-chef-11-1-3-release/
http://www.getchef.com/blog/2014/04/09/enterprise-chef-1-4-9-release/
http://www.getchef.com/blog/2014/04/09/chef-server-11-0-12-release/
http://twitter.com/agl__/statuses/437029812046422016
http://support.apple.com/kb/HT6150
http://secunia.com/advisories/57968
http://secunia.com/advisories/57966