diff --git a/application/src/main/java/org/thingsboard/server/controller/AlarmController.java b/application/src/main/java/org/thingsboard/server/controller/AlarmController.java
index 78ee6620fe..54368af0db 100644
--- a/application/src/main/java/org/thingsboard/server/controller/AlarmController.java
+++ b/application/src/main/java/org/thingsboard/server/controller/AlarmController.java
@@ -139,6 +139,9 @@ public class AlarmController extends BaseController {
         checkNotNull(alarm.getOriginator());
         checkEntity(alarm.getId(), alarm, Resource.ALARM);
         checkEntityId(alarm.getOriginator(), Operation.READ);
+        if (alarm.getAssigneeId() != null) {
+            checkUserId(alarm.getAssigneeId(), Operation.READ);
+        }
         return tbAlarmService.save(alarm, getCurrentUser());
     }
 
diff --git a/application/src/main/java/org/thingsboard/server/service/entitiy/alarm/DefaultTbAlarmService.java b/application/src/main/java/org/thingsboard/server/service/entitiy/alarm/DefaultTbAlarmService.java
index e452a766a4..b4ac7117c8 100644
--- a/application/src/main/java/org/thingsboard/server/service/entitiy/alarm/DefaultTbAlarmService.java
+++ b/application/src/main/java/org/thingsboard/server/service/entitiy/alarm/DefaultTbAlarmService.java
@@ -70,7 +70,7 @@ public class DefaultTbAlarmService extends AbstractTbEntityService implements Tb
             UserId newAssignee = alarm.getAssigneeId();
             UserId curAssignee = resultAlarm.getAssigneeId();
             if (newAssignee != null && !newAssignee.equals(curAssignee)) {
-                resultAlarm = assign(alarm, newAssignee, alarm.getAssignTs(), user);
+                resultAlarm = assign(resultAlarm, newAssignee, alarm.getAssignTs(), user);
             } else if (newAssignee == null && curAssignee != null) {
                 resultAlarm = unassign(alarm, alarm.getAssignTs(), user);
             }
diff --git a/application/src/test/java/org/thingsboard/server/controller/AbstractWebTest.java b/application/src/test/java/org/thingsboard/server/controller/AbstractWebTest.java
index c9b739bad1..f0e3972200 100644
--- a/application/src/test/java/org/thingsboard/server/controller/AbstractWebTest.java
+++ b/application/src/test/java/org/thingsboard/server/controller/AbstractWebTest.java
@@ -352,6 +352,7 @@ public abstract class AbstractWebTest extends AbstractInMemoryStorageTest {
     protected Tenant savedDifferentTenant;
     protected User savedDifferentTenantUser;
     private Customer savedDifferentCustomer;
+    protected User differentCustomerUser;
 
     protected void loginDifferentTenant() throws Exception {
         if (savedDifferentTenant != null) {
@@ -379,7 +380,7 @@ public abstract class AbstractWebTest extends AbstractInMemoryStorageTest {
             createDifferentCustomer();
 
             loginTenantAdmin();
-            User differentCustomerUser = new User();
+            differentCustomerUser = new User();
             differentCustomerUser.setAuthority(Authority.CUSTOMER_USER);
             differentCustomerUser.setTenantId(tenantId);
             differentCustomerUser.setCustomerId(savedDifferentCustomer.getId());
diff --git a/application/src/test/java/org/thingsboard/server/controller/BaseAlarmControllerTest.java b/application/src/test/java/org/thingsboard/server/controller/BaseAlarmControllerTest.java
index 6a94cc5a1e..7cf6d7109a 100644
--- a/application/src/test/java/org/thingsboard/server/controller/BaseAlarmControllerTest.java
+++ b/application/src/test/java/org/thingsboard/server/controller/BaseAlarmControllerTest.java
@@ -656,4 +656,38 @@ public abstract class BaseAlarmControllerTest extends AbstractControllerTest {
 
         return foundAlarm;
     }
+
+
+    @Test
+    public void testCreateAlarmWithOtherTenantsAssignee() throws Exception {
+        loginDifferentTenant();
+        loginTenantAdmin();
+
+        Alarm alarm = Alarm.builder()
+                .tenantId(tenantId)
+                .customerId(customerId)
+                .originator(customerDevice.getId())
+                .severity(AlarmSeverity.CRITICAL)
+                .assigneeId(savedDifferentTenantUser.getId())
+                .build();
+
+        doPost("/api/alarm", alarm).andExpect(status().isForbidden());
+    }
+
+    @Test
+    public void testCreateAlarmWithOtherCustomerAsAssignee() throws Exception {
+        loginDifferentCustomer();
+        loginCustomerUser();
+
+        Alarm alarm = Alarm.builder()
+                .tenantId(tenantId)
+                .customerId(customerId)
+                .originator(customerDevice.getId())
+                .severity(AlarmSeverity.CRITICAL)
+                .assigneeId(differentCustomerUser.getId())
+                .build();
+
+        doPost("/api/alarm", alarm).andExpect(status().isForbidden());
+    }
+
 }