OpenStack keystonemiddleware (formerly python-keystoneclient) 0.x before 0.11.0 and 1.x before 1.2.0 disables certification verification when the "insecure" option is set in a paste configuration (paste.ini) file regardless of the value, which allows remote attackers to conduct man-in-the-middle attacks via a crafted certificate.
It was discovered that some items in the S3Token paste configuration as used by python-keystonemiddleware (formerly python-keystoneclient) were incorrectly evaluated as strings, an issue similar to CVE-2014-7144. If the "insecure" option were set to "false", the option would be evaluated as true, resulting in TLS connections being vulnerable to man-in-the-middle attacks. Note: the "insecure" option defaults to false, so setups that do not specifically define "insecure=false" are not affected.