diff --git a/modules/cpr/src/main/java/org/atmosphere/container/JSR356Endpoint.java b/modules/cpr/src/main/java/org/atmosphere/container/JSR356Endpoint.java
index 537aa1e012..e201431bae 100644
--- a/modules/cpr/src/main/java/org/atmosphere/container/JSR356Endpoint.java
+++ b/modules/cpr/src/main/java/org/atmosphere/container/JSR356Endpoint.java
@@ -225,11 +225,13 @@ public void onOpen(Session session, final EndpointConfig endpointConfig) {
                     cookies.addAll(CookieUtil.ServerCookieDecoder.STRICT.decode(cookieHeader));
             }
 
-            Enumeration<String> attributeNames = handshakeSession.getAttributeNames();
-            Map<String, Object> attributes = new ConcurrentHashMap<>();
-            while (attributeNames.hasMoreElements()) {
-                String attributeName = attributeNames.nextElement();
-                attributes.put(attributeName, handshakeSession.getAttribute(attributeName));
+            final Map<String, Object> attributes = new ConcurrentHashMap<>();
+            if (handshakeSession != null) {
+                Enumeration<String> attributeNames = handshakeSession.getAttributeNames();
+                while (attributeNames.hasMoreElements()) {
+                    String attributeName = attributeNames.nextElement();
+                    attributes.put(attributeName, handshakeSession.getAttribute(attributeName));
+                }
             }
 
             request = new AtmosphereRequestImpl.Builder()
diff --git a/modules/cpr/src/test/java/org/atmosphere/container/version/JSR356WebSocketTest.java b/modules/cpr/src/test/java/org/atmosphere/container/version/JSR356WebSocketTest.java
index a6bfeda700..9772863553 100644
--- a/modules/cpr/src/test/java/org/atmosphere/container/version/JSR356WebSocketTest.java
+++ b/modules/cpr/src/test/java/org/atmosphere/container/version/JSR356WebSocketTest.java
@@ -23,29 +23,34 @@
 import jakarta.websocket.SendResult;
 import jakarta.websocket.Session;
 import jakarta.websocket.server.HandshakeRequest;
+import jakarta.websocket.server.ServerEndpointConfig;
 import org.atmosphere.container.JSR356Endpoint;
-import org.atmosphere.cpr.ApplicationConfig;
 import org.atmosphere.cpr.AtmosphereConfig;
 import org.atmosphere.cpr.AtmosphereFramework;
 import org.atmosphere.cpr.AtmosphereRequest;
 import org.atmosphere.websocket.WebSocketProcessor;
+import org.mockito.Mockito;
 import org.mockito.invocation.InvocationOnMock;
 import org.mockito.stubbing.Answer;
 import org.testng.annotations.BeforeMethod;
 import org.testng.annotations.Test;
 
+import java.io.IOException;
 import java.lang.reflect.Field;
 import java.net.URI;
+import java.util.Collections;
 import java.util.Enumeration;
 import java.util.HashMap;
 import java.util.Map;
 import java.util.Vector;
 
+import static org.atmosphere.cpr.ApplicationConfig.JSR356_MAPPING_PATH;
 import static org.mockito.ArgumentMatchers.any;
 import static org.mockito.ArgumentMatchers.anyString;
 import static org.mockito.ArgumentMatchers.eq;
 import static org.mockito.Mockito.doAnswer;
 import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.never;
 import static org.mockito.Mockito.times;
 import static org.mockito.Mockito.verify;
 import static org.mockito.Mockito.when;
@@ -157,10 +162,9 @@ public void testAttributePropagationFromHandshakeSessionToAtmosphereRequest() th
         AtmosphereFramework mockFramework = mock(AtmosphereFramework.class);
         AtmosphereConfig mockConfig = mock(AtmosphereConfig.class);
 
-        // Stub the getAtmosphereConfig and getInitParameter methods
         when(mockFramework.getAtmosphereConfig()).thenReturn(mockConfig);
         when(mockFramework.getServletContext()).thenReturn(mock(ServletContext.class));
-        when(mockConfig.getInitParameter(ApplicationConfig.JSR356_MAPPING_PATH)).thenReturn("/");
+        when(mockConfig.getInitParameter(JSR356_MAPPING_PATH)).thenReturn("/");
         when(mockConfig.getServletContext()).thenReturn(mock(ServletContext.class));
 
         WebSocketProcessor webSocketProcessor = mock(WebSocketProcessor.class);
@@ -180,4 +184,42 @@ public void testAttributePropagationFromHandshakeSessionToAtmosphereRequest() th
                     "Attribute value should match the value from the HttpSession");
         }
     }
+
+    @Test
+    public void testOnOpenWithNullHandshakeSession() throws IOException {
+        Session mockSession = Mockito.mock(Session.class);
+        HandshakeRequest mockHandshakeRequest = Mockito.mock(HandshakeRequest.class);
+        ServerEndpointConfig mockConfig = Mockito.mock(ServerEndpointConfig.class);
+        WebSocketProcessor mockProcessor = Mockito.mock(WebSocketProcessor.class);
+        RemoteEndpoint.Async mockAsyncRemote = Mockito.mock(RemoteEndpoint.Async.class);
+
+        AtmosphereFramework mockFramework = mock(AtmosphereFramework.class);
+        AtmosphereConfig mockAtmosphereConfig = mock(AtmosphereConfig.class);
+
+        when(mockProcessor.handshake(Mockito.any(AtmosphereRequest.class))).thenReturn(true);
+        when(mockFramework.getAtmosphereConfig()).thenReturn(mockAtmosphereConfig);
+        when(mockFramework.getServletContext()).thenReturn(mock(ServletContext.class));
+        when(mockAtmosphereConfig.getInitParameter(JSR356_MAPPING_PATH)).thenReturn("/");
+        when(mockAtmosphereConfig.getServletContext()).thenReturn(mock(ServletContext.class));
+        when(mockFramework.getAtmosphereConfig()).thenReturn(mockAtmosphereConfig);
+        when(mockFramework.getServletContext()).thenReturn(mock(ServletContext.class));
+        when(mockAtmosphereConfig.getInitParameter(JSR356_MAPPING_PATH)).thenReturn("/");
+        when(mockAtmosphereConfig.getServletContext()).thenReturn(mock(ServletContext.class));
+
+        JSR356Endpoint endpoint = new JSR356Endpoint(mockFramework, mockProcessor);
+
+        when(mockSession.getAsyncRemote()).thenReturn(mockAsyncRemote);
+        when(mockSession.isOpen()).thenReturn(true);
+        when(mockSession.getRequestURI()).thenReturn(URI.create("/"));
+
+        when(mockHandshakeRequest.getHttpSession()).thenReturn(null);
+        when(mockHandshakeRequest.getHeaders()).thenReturn(Collections.emptyMap());
+
+        endpoint.handshakeRequest(mockHandshakeRequest);
+
+        endpoint.onOpen(mockSession, mockConfig);
+
+        verify(mockSession, never()).close(Mockito.any());
+
+    }
 }
\ No newline at end of file