The checkPassword function in python-kerberos does not authenticate the KDC it attempts to communicate with, which allows remote attackers to cause a denial of service (bad response), or have other unspecified impact by performing a man-in-the-middle attack.
https://pypi.python.org/pypi/kerberos
https://github.com/apple/ccs-pykerberos/issues/31
https://bugzilla.redhat.com/show_bug.cgi?id=1223802