Apache Commons HttpClient 3.x, as used in Amazon Flexible Payments Service (FPS) merchant Java SDK and other products, 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.
https://issues.apache.org/jira/browse/HTTPCLIENT-1265
https://exchange.xforce.ibmcloud.com/vulnerabilities/79984
https://access.redhat.com/errata/RHSA-2017:0868
http://www.ubuntu.com/usn/USN-2769-1