Getting "SSLPeerUnverifiedException: peer not authenticated" error in JBoss EAP when making outbound SSL call to an external backend service

Issue

• The following error is thrown in the server.log file:

  ...
  05:45:15,311 INFO  [stdout] (http-/0.0.0.0:12412-4) http-/0.0.0.0:12412-4, handling exception: javax.net.ssl.SSLHandshakeException: sun.security.validator.ValidatorException: PKIX path building failed: sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification path to requested target
  05:45:15,311 INFO  [stdout] (http-/0.0.0.0:12412-4) http-/0.0.0.0:12412-4, IOException in getSession():  javax.net.ssl.SSLHandshakeException: sun.security.validator.ValidatorException: PKIX path building failed: sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification path to requested target
  05:45:15,311 INFO  [stdout] (http-/0.0.0.0:12412-4) http-/0.0.0.0:12412-4, called close()
  05:45:15,311 INFO  [stdout] (http-/0.0.0.0:12412-4) http-/0.0.0.0:12412-4, called closeInternal(true)
  05:45:15,311 INFO  [stdout] (http-/0.0.0.0:12412-4) http-/0.0.0.0:12412-4, called close()
  05:45:15,311 INFO  [stdout] (http-/0.0.0.0:12412-4) http-/0.0.0.0:12412-4, called closeInternal(true)
  05:45:15,313 INFO  [stdout] (http-/0.0.0.0:12412-4) 2016-12-08 05:45:15,312 [http-/0.0.0.0:12412-4] ERROR EXCEPTION.com.XXXX.some.custom.code.servlet.YYYY - <152> Caught exception: javax.net.ssl.SSLPeerUnverifiedException: peer not authenticated
  05:45:15,313 INFO  [stdout] (http-/0.0.0.0:12412-4) javax.net.ssl.SSLPeerUnverifiedException: peer not authenticated
  05:45:15,313 INFO  [stdout] (http-/0.0.0.0:12412-4)     at sun.security.ssl.SSLSessionImpl.getPeerCertificates(SSLSessionImpl.java:421)
  05:45:15,313 INFO  [stdout] (http-/0.0.0.0:12412-4)     at org.apache.http.conn.ssl.AbstractVerifier.verify(AbstractVerifier.java:128)
  05:45:15,313 INFO  [stdout] (http-/0.0.0.0:12412-4)     at org.apache.http.conn.ssl.SSLSocketFactory.connectSocket(SSLSocketFactory.java:397)
  ...
  ** <!-- SEE HERE: #BEGIN
  
  05:45:15,313 INFO  [stdout] (http-/0.0.0.0:12412-4)     at com.XXXX.some.custom.code.servlet.YYYY.someMethod(YYYY.java:1767)
  05:45:15,313 INFO  [stdout] (http-/0.0.0.0:12412-4)     at com.XXXX.some.custom.code.servlet.YYYY.doPost(YYYY.java:1019)
  
  ** SEE HERE #END -->
  05:45:15,313 INFO  [stdout] (http-/0.0.0.0:12412-4)     at javax.servlet.http.HttpServlet.service(HttpServlet.java:754)
  05:45:15,313 INFO  [stdout] (http-/0.0.0.0:12412-4)     at javax.servlet.http.HttpServlet.service(HttpServlet.java:847)
  05:45:15,313 INFO  [stdout] (http-/0.0.0.0:12412-4)     at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:295)
  05:45:15,313 INFO  [stdout] (http-/0.0.0.0:12412-4)     at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:214)
  05:45:15,313 INFO  [stdout] (http-/0.0.0.0:12412-4)     at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:230)
  ...