diff --git a/components/extensions/emqx-extensions/io.entgra.device.mgt.plugins.emqx.exhook/src/main/java/io/entgra/device/mgt/plugins/emqx/exhook/ExServer.java b/components/extensions/emqx-extensions/io.entgra.device.mgt.plugins.emqx.exhook/src/main/java/io/entgra/device/mgt/plugins/emqx/exhook/ExServer.java
index 0d5d3d3a7..c297c885d 100644
--- a/components/extensions/emqx-extensions/io.entgra.device.mgt.plugins.emqx.exhook/src/main/java/io/entgra/device/mgt/plugins/emqx/exhook/ExServer.java
+++ b/components/extensions/emqx-extensions/io.entgra.device.mgt.plugins.emqx.exhook/src/main/java/io/entgra/device/mgt/plugins/emqx/exhook/ExServer.java
@@ -44,13 +44,14 @@ import org.wso2.carbon.context.PrivilegedCarbonContext;
 
 import java.io.IOException;
 import java.util.*;
+import java.util.concurrent.ConcurrentHashMap;
 import java.util.concurrent.TimeUnit;
 
 public class ExServer {
     private static final Log logger = LogFactory.getLog(ExServer.class.getName());
 
-    private static Map<String, String> accessTokenMap = new HashMap<>();
-    private static Map<String, String> authorizedScopeMap = new HashMap<>();
+    private static Map<String, String> accessTokenMap = new ConcurrentHashMap<>();
+    private static Map<String, String> authorizedScopeMap = new ConcurrentHashMap<>();
     private Server server;
 
     public ExServer() {
@@ -177,25 +178,27 @@ public class ExServer {
             if (request.getResultCode().equals("success")) {
                 String accessToken = accessTokenMap.get(request.getConninfo().getClientid());
                 String scopeString = authorizedScopeMap.get(accessToken);
-                String[] scopeArray = scopeString.split(" ");
-                String deviceType = null;
-                String deviceId = null;
-                for (String scope : scopeArray) {
-                    if (scope.startsWith("device_")) {
-                        String[] scopeParts = scope.split("_");
-                        deviceType = scopeParts[1];
-                        deviceId = scopeParts[2];
-                        break;
+                if (!StringUtils.isEmpty(scopeString)) {
+                    String[] scopeArray = scopeString.split(" ");
+                    String deviceType = null;
+                    String deviceId = null;
+                    for (String scope : scopeArray) {
+                        if (scope.startsWith("device_")) {
+                            String[] scopeParts = scope.split("_");
+                            deviceType = scopeParts[1];
+                            deviceId = scopeParts[2];
+                            break;
+                        }
                     }
-                }
-                if (!StringUtils.isEmpty(deviceType) && !StringUtils.isEmpty(deviceId)) {
-                    try {
-                        PrivilegedCarbonContext.getThreadLocalCarbonContext().setTenantDomain("carbon.super");
-                        PrivilegedCarbonContext.getThreadLocalCarbonContext().setTenantId(-1234);
-                        DeviceManagementProviderService deviceManagementProviderService = getDeviceManagementService();
-                        deviceManagementProviderService.changeDeviceStatus(new DeviceIdentifier(deviceId, deviceType), EnrolmentInfo.Status.ACTIVE);
-                    } catch (DeviceManagementException e) {
-                        logger.error("onClientConnack: Error while setting device status");
+                    if (!StringUtils.isEmpty(deviceType) && !StringUtils.isEmpty(deviceId)) {
+                        try {
+                            PrivilegedCarbonContext.getThreadLocalCarbonContext().setTenantDomain("carbon.super");
+                            PrivilegedCarbonContext.getThreadLocalCarbonContext().setTenantId(-1234);
+                            DeviceManagementProviderService deviceManagementProviderService = getDeviceManagementService();
+                            deviceManagementProviderService.changeDeviceStatus(new DeviceIdentifier(deviceId, deviceType), EnrolmentInfo.Status.ACTIVE);
+                        } catch (DeviceManagementException e) {
+                            logger.error("onClientConnack: Error while setting device status");
+                        }
                     }
                 }
             }
@@ -315,53 +318,57 @@ public class ExServer {
                 if (StringUtils.isEmpty(accessToken) || !accessToken.startsWith(request.getClientinfo().getUsername())) {
                     logger.info("Valid access token not found");
                     responseObserver.onError(new Exception("not authorized"));
+                    return;
                 }
 
                 String authorizedScopeList = authorizedScopeMap.get(accessToken);
-                String[] scopeArray = authorizedScopeList.split(" ");
-                List<String> scopeList = Arrays.asList(scopeArray);
                 boolean isFound = false;
+                if (!StringUtils.isEmpty(authorizedScopeList)) {
+                    String[] scopeArray = authorizedScopeList.split(" ");
+                    List<String> scopeList = Arrays.asList(scopeArray);
 
-                String tempScope = null;
-                String requestTopic = request.getTopic();
 
-                if (request.getType().equals(ClientCheckAclRequest.AclReqType.PUBLISH)) {
-                    requestTopic = requestTopic.replace("/", ":");
+                    String tempScope = null;
+                    String requestTopic = request.getTopic();
 
-                    String[] requestTopicParts = requestTopic.split(":");
+                    if (request.getType().equals(ClientCheckAclRequest.AclReqType.PUBLISH)) {
+                        requestTopic = requestTopic.replace("/", ":");
 
-                    if (requestTopicParts.length >= 4 && "operation".equals(requestTopicParts[3])) {
-                        // publishing operation from iot server to emqx
-                        tempScope = "perm:topic:pub:" + requestTopicParts[0] + ":+:+:operation";
-                    } else {
-                        // publishing operation response from device to emqx
-                        // publishing events from device to emqx
-                        tempScope = "perm:topic:pub:" + requestTopic;
-                    }
+                        String[] requestTopicParts = requestTopic.split(":");
 
-                    for (String scope : scopeList) {
-                        if (scope.startsWith(tempScope)) {
-                            isFound = true;
-                            break;
+                        if (requestTopicParts.length >= 4 && "operation".equals(requestTopicParts[3])) {
+                            // publishing operation from iot server to emqx
+                            tempScope = "perm:topic:pub:" + requestTopicParts[0] + ":+:+:operation";
+                        } else {
+                            // publishing operation response from device to emqx
+                            // publishing events from device to emqx
+                            tempScope = "perm:topic:pub:" + requestTopic;
                         }
-                    }
-                }
 
-                if (request.getType().equals(ClientCheckAclRequest.AclReqType.SUBSCRIBE)) {
-                    if (requestTopic.endsWith("/#")) {
-                        requestTopic = requestTopic.substring(0, requestTopic.indexOf("/#"));
+                        for (String scope : scopeList) {
+                            if (scope.startsWith(tempScope)) {
+                                isFound = true;
+                                break;
+                            }
+                        }
                     }
 
-                    requestTopic = requestTopic.replace("/", ":");
-                    // subscribing for events from iotserver to emqx
-                    // subscribing for operation from device to emqx
-                    // subscribing for operation response from iotserver to emqx
-                    tempScope = "perm:topic:sub:" + requestTopic;
+                    if (request.getType().equals(ClientCheckAclRequest.AclReqType.SUBSCRIBE)) {
+                        if (requestTopic.endsWith("/#")) {
+                            requestTopic = requestTopic.substring(0, requestTopic.indexOf("/#"));
+                        }
 
-                    for (String scope : scopeList) {
-                        if (scope.startsWith(tempScope)) {
-                            isFound = true;
-                            break;
+                        requestTopic = requestTopic.replace("/", ":");
+                        // subscribing for events from iotserver to emqx
+                        // subscribing for operation from device to emqx
+                        // subscribing for operation response from iotserver to emqx
+                        tempScope = "perm:topic:sub:" + requestTopic;
+
+                        for (String scope : scopeList) {
+                            if (scope.startsWith(tempScope)) {
+                                isFound = true;
+                                break;
+                            }
                         }
                     }
                 }