upgrade Jetty to 9.4.21.v20190926
diff --git a/pom.xml b/pom.xml
index 70667aa..b2dc99c 100644
--- a/pom.xml
+++ b/pom.xml
@@ -57,7 +57,7 @@
         <javax.el.version>3.0.0</javax.el.version>
         <javax.validation.version>2.0.1.Final</javax.validation.version>
         <jaxb.version>2.3.2</jaxb.version>
-        <jetty9.version>9.4.20.v20190813</jetty9.version>
+        <jetty9.version>9.4.21.v20190926</jetty9.version>
         <junit.version>4.12</junit.version>
         <kerby.version>1.1.1</kerby.version>
         <log4j.version>1.2.17</log4j.version>