Async Http Client (aka AHC or async-http-client) before 1.9.0 skips X.509 certificate verification unless both a keyStore location and a trustStore location are explicitly set, which allows man-in-the-middle attackers to spoof HTTPS servers by presenting an arbitrary certificate during use of a typical AHC configuration, as demonstrated by a configuration that does not send client certificates.
https://wiki.jenkins-ci.org/display/SECURITY/Jenkins+Security+Advisory+2016-06-20
https://github.com/AsyncHttpClient/async-http-client/issues/352
http://www.securityfocus.com/bid/69316
http://rhn.redhat.com/errata/RHSA-2015-1551.html
http://rhn.redhat.com/errata/RHSA-2015-1176.html
http://rhn.redhat.com/errata/RHSA-2015-0851.html