diff --git a/apps/backend/.env-example b/apps/backend/.env-example
index 8bf9db4713..1a3d724fa2 100644
--- a/apps/backend/.env-example
+++ b/apps/backend/.env-example
@@ -38,6 +38,10 @@ DATABASE_SSL_CA=<Full path to SSL certificate authority OR the certificate autho
 ## Reverse proxy
 NGINX_HOST=<Templated out as the 'server_name' for the NGINX configuration (no default, must be set if using the provided example NGINX configuration)>
 
+## External interfaces 
+SPLUNK_HOST_URL=<The full Uniform Resource Locator (URL) without the port for the Splunk host (no default, must be set if connecting to Splunk)>
+TENABLE_HOST_URL=<The full Uniform Resource Locator (URL) without the port for the Tenable.SC host (no default, must be set if connecting to Tenable)>
+
 # Authentication
 
 EXTERNAL_URL=<The external URL for your Heimdall deployment, for example https://heimdall.mitre.org>
diff --git a/apps/backend/config/app_config.ts b/apps/backend/config/app_config.ts
index 44635051f5..b5066078a8 100644
--- a/apps/backend/config/app_config.ts
+++ b/apps/backend/config/app_config.ts
@@ -35,6 +35,24 @@ export default class AppConfig {
     return process.env[key] || this.envConfig[key];
   }
 
+  getSplunkHostUrl(): string {
+    const splunk_host_url = this.get('SPLUNK_HOST_URL');
+    if (splunk_host_url !== undefined) {
+      return splunk_host_url;
+    } else {
+      return '';
+    }
+  }
+
+  getTenableHostUrl(): string {
+    const tenable_host_url = this.get('TENABLE_HOST_URL');
+    if (tenable_host_url !== undefined) {
+      return tenable_host_url;
+    } else {
+      return '';
+    }
+  }
+
   getDatabaseName(): string {
     const databaseName = this.get('DATABASE_NAME');
     const nodeEnvironment = this.get('NODE_ENV');
diff --git a/apps/backend/src/config/config.service.ts b/apps/backend/src/config/config.service.ts
index 2275a9715f..3bef773e05 100644
--- a/apps/backend/src/config/config.service.ts
+++ b/apps/backend/src/config/config.service.ts
@@ -57,10 +57,20 @@ export class ConfigService {
       oidcName: this.get('OIDC_NAME') || '',
       ldap: this.get('LDAP_ENABLED')?.toLocaleLowerCase() === 'true' || false,
       registrationEnabled: this.isRegistrationAllowed(),
-      localLoginEnabled: this.isLocalLoginAllowed()
+      localLoginEnabled: this.isLocalLoginAllowed(),
+      tenableHostUrl: this.getTenableHostUrl(),
+      splunkHostUrl: this.getSplunkHostUrl()
     });
   }
 
+  getSplunkHostUrl(): string {
+    return this.appConfig.getSplunkHostUrl();
+  }
+
+  getTenableHostUrl(): string {
+    return this.appConfig.getTenableHostUrl();
+  }
+
   getDbConfig(): SequelizeOptions {
     return this.appConfig.getDbConfig();
   }
diff --git a/apps/backend/src/config/dto/startup-settings.dto.ts b/apps/backend/src/config/dto/startup-settings.dto.ts
index c6069b5597..6329e3c9ba 100644
--- a/apps/backend/src/config/dto/startup-settings.dto.ts
+++ b/apps/backend/src/config/dto/startup-settings.dto.ts
@@ -11,6 +11,8 @@ export class StartupSettingsDto implements IStartupSettings {
   readonly ldap: boolean;
   readonly registrationEnabled: boolean;
   readonly localLoginEnabled: boolean;
+  readonly tenableHostUrl: string;
+  readonly splunkHostUrl: string;
 
   constructor(settings: IStartupSettings) {
     this.apiKeysEnabled = settings.apiKeysEnabled;
@@ -23,5 +25,7 @@ export class StartupSettingsDto implements IStartupSettings {
     this.ldap = settings.ldap;
     this.registrationEnabled = settings.registrationEnabled;
     this.localLoginEnabled = settings.localLoginEnabled;
+    this.tenableHostUrl = settings.tenableHostUrl;
+    this.splunkHostUrl = settings.splunkHostUrl;
   }
 }
diff --git a/apps/backend/src/main.ts b/apps/backend/src/main.ts
index 8b92c75b95..9d9ecf76d8 100644
--- a/apps/backend/src/main.ts
+++ b/apps/backend/src/main.ts
@@ -40,8 +40,10 @@ async function bootstrap() {
         'connect-src': [
           "'self'",
           'https://api.github.com',
-          'https://sts.amazonaws.com'
-        ]
+          'https://sts.amazonaws.com',
+          configService.getTenableHostUrl(),
+          configService.getSplunkHostUrl()
+        ].filter((source) => source)
       }
     })
   );
diff --git a/apps/frontend/src/components/global/upload_tabs/tenable/AuthStep.vue b/apps/frontend/src/components/global/upload_tabs/tenable/AuthStep.vue
index 5622990c43..48991f7ef9 100644
--- a/apps/frontend/src/components/global/upload_tabs/tenable/AuthStep.vue
+++ b/apps/frontend/src/components/global/upload_tabs/tenable/AuthStep.vue
@@ -2,6 +2,7 @@
   <div>
     <v-form>
       <v-text-field
+        ref="access_Key"
         v-model="accesskey"
         label="Access Token (Key)"
         for="accesskey_field"
@@ -9,6 +10,7 @@
         data-cy="tenableaccesskey"
       />
       <v-text-field
+        ref="secret_Key"
         v-model="secretkey"
         label="Secret Token (Key)"
         for="secretkey_field"
@@ -18,6 +20,7 @@
         data-cy="tenablesecretkey"
       />
       <v-text-field
+        ref="hostname_value"
         v-model="hostname"
         label="Hostname"
         for="hostname_field"
@@ -70,14 +73,40 @@ export default class AuthStep extends Vue {
   secretkey = '';
   hostname = '';
 
+  $refs!: {
+    access_Key: HTMLInputElement;
+    secret_Key: HTMLAnchorElement;
+    hostname_value: HTMLAnchorElement;
+  };
+
   // Form required field rule
   reqRule = requireFieldRule;
 
   async login(): Promise<void> {
+    if (!this.accesskey) {
+      SnackbarModule.failure('The Access Token (key) is required');
+      this.$refs.access_Key.focus();
+      return;
+    } else if (!this.secretkey) {
+      SnackbarModule.failure('The Secret Token (key) is required');
+      this.$refs.secret_Key.focus();
+      return;
+    } else if (!this.hostname) {
+      SnackbarModule.failure('The Tenable.Sc URL is required');
+      this.$refs.hostname_value.focus();
+      return;
+    }
+
+    // If the protocol (https) is missing add it
     if (!/^https?:\/\//.test(this.hostname)) {
       this.hostname = `https://${this.hostname}`;
     }
 
+    // If the SSL/TLS port is missing add default 443
+    if (!this.hostname.split(':')[2]) {
+      this.hostname = `${this.hostname}:443`;
+    }
+
     const config: AuthInfo = {
       accesskey: this.accesskey,
       secretkey: this.secretkey,
diff --git a/apps/frontend/src/components/global/upload_tabs/tenable/TenableReader.vue b/apps/frontend/src/components/global/upload_tabs/tenable/TenableReader.vue
index 8bb165bf2c..b516071805 100644
--- a/apps/frontend/src/components/global/upload_tabs/tenable/TenableReader.vue
+++ b/apps/frontend/src/components/global/upload_tabs/tenable/TenableReader.vue
@@ -41,7 +41,7 @@
           </span>
           <br />
           <span>
-            For connection instructions and further information, check here:
+            For connection instructions and further information, consult:
           </span>
           <v-btn
             target="_blank"
diff --git a/apps/frontend/src/store/server.ts b/apps/frontend/src/store/server.ts
index 1298414cd3..c617028c8c 100644
--- a/apps/frontend/src/store/server.ts
+++ b/apps/frontend/src/store/server.ts
@@ -35,6 +35,8 @@ export interface IServerState {
   ldap: boolean;
   localLoginEnabled: boolean;
   userInfo: IUser;
+  tenableHostUrl: string;
+  splunkHostUrl: string;
 }
 
 interface LoginData {
@@ -63,6 +65,8 @@ class Server extends VuexModule implements IServerState {
   enabledOAuth: string[] = [];
   allUsers: ISlimUser[] = [];
   oidcName = '';
+  tenableHostUrl: string = '';
+  splunkHostUrl: string = '';
   /** Our currently granted JWT token */
   token = '';
   /** Provide a sane default for userInfo in order to avoid having to null check it all the time */
@@ -106,6 +110,8 @@ class Server extends VuexModule implements IServerState {
     this.oidcName = settings.oidcName;
     this.ldap = settings.ldap;
     this.localLoginEnabled = settings.localLoginEnabled;
+    this.tenableHostUrl = settings.tenableHostUrl;
+    this.splunkHostUrl = settings.splunkHostUrl;
   }
 
   @Mutation
diff --git a/apps/frontend/src/utilities/tenable_util.ts b/apps/frontend/src/utilities/tenable_util.ts
index 7566f3af5e..10f195380a 100644
--- a/apps/frontend/src/utilities/tenable_util.ts
+++ b/apps/frontend/src/utilities/tenable_util.ts
@@ -1,5 +1,6 @@
 import Zip from 'adm-zip';
 import axios, {AxiosInstance} from 'axios';
+import {ServerModule} from '@/store/server';
 import {createWinstonLogger} from '../../../../libs/hdf-converters/src/utils/global';
 
 /** represents the information of the current used */
@@ -49,7 +50,7 @@ export class TenableUtil {
         () =>
           reject(
             new Error(
-              'Login timed out. Please check your CORS configuration or validate you have inputted the correct domain'
+              'Login timed out. Please ensure the provided credentials and domain/URL are valid and try again.'
             )
           ),
         5000
@@ -64,21 +65,7 @@ export class TenableUtil {
             resolve(response.request.finished);
           })
           .catch((error) => {
-            try {
-              if (error.code == 'ENOTFOUND') {
-                reject(
-                  `Host: ${this.hostConfig.host_url} not found, check the Host Name (URL) or the network`
-                );
-              } else if (error.response.data.error_code == 74) {
-                reject('Incorrect Access or Secret key');
-              } else {
-                reject(error.response.data.error_msg);
-              }
-            } catch (e) {
-              reject(
-                `Possible network connection blocked by CORS policy. Received error: ${error}`
-              );
-            }
+            reject(this.getRejectConnectionMessage(error));
           });
       } catch (e) {
         reject(`Unknown error: ${e}`);
@@ -86,6 +73,63 @@ export class TenableUtil {
     });
   }
 
+  // eslint-disable-next-line @typescript-eslint/no-explicit-any
+  getRejectConnectionMessage(error: any): string {
+    let rejectMsg = '';
+
+    if (error.response) {
+      // The request was made and the server responded with a status code
+      // that falls out of the range of 2xx
+
+      if (error.response.data.error_code == 74) {
+        rejectMsg = 'Incorrect Access or Secret key';
+      } else {
+        rejectMsg = `${error.name} : ${error.response.data.error_msg}`;
+      }
+    } else if (error.request) {
+      // The request was made but no response was received.
+      // `error.request` is an instance of XMLHttpRequest in the
+      // browser and an instance of http.ClientRequest in node.js
+
+      if (error.code == 'ERR_NETWORK') {
+        // Check if the tenable url was provided - Content Security Policy (CSP)
+        const corsReject = `Access blocked by CORS or connection refused by the host: ${error.config.baseURL}. See Help for additional instructions.`;
+        const tenableUrl = ServerModule.tenableHostUrl;
+        if (tenableUrl) {
+          // If the URL is listed in the allows domains
+          // (.env variable TENABLE_HOST_URL) check if they match
+          if (!error.config.baseURL.includes(tenableUrl)) {
+            rejectMsg = `Hostname: ${error.config.baseURL} violates the Content Security Policy (CSP). The host allowed by the CSP is: ${tenableUrl}`;
+          } else {
+            // CSP url did match, check for port match - reject appropriately
+            const portNumber = parseInt(this.hostConfig.host_url.split(':')[2]);
+            if (portNumber != 443) {
+              rejectMsg = `Invalid SSL/TSL port number used: ${portNumber} must be 443.`;
+            } else {
+              rejectMsg = corsReject;
+            }
+          }
+        } else if (ServerModule.serverMode) {
+          // The URL is not listed in the allows domains (CSP) and Heimdall instance is a server
+          rejectMsg =
+            'The Content Security Policy directive environment variable "TENABLE_HOST_URL" not configured. See Help for additional instructions.';
+        } else {
+          rejectMsg = corsReject;
+        }
+      } else if (error.code == 'ENOTFOUND') {
+        rejectMsg = `Host: ${error.config.baseURL} not found, check the Hostname (URL) or the network.`;
+      } else if (error.code == 'ERR_CONNECTION_REFUSED') {
+        rejectMsg = `Received network connection refused by the host: ${error.config.baseURL}`;
+      } else {
+        rejectMsg = `${error.name} : ${error.message}`;
+      }
+    } else {
+      // Something happened in setting up the request that triggered an Error
+      rejectMsg = `${error.name} : ${error.message}`;
+    }
+    return rejectMsg;
+  }
+
   /**
    * Gets the list of Scan Results.
    * Returned values are based on the fields requested:
@@ -98,7 +142,7 @@ export class TenableUtil {
         () =>
           reject(
             new Error(
-              'Login timed out. Please check your CORS configuration or validate you have inputted the correct domain'
+              'Login timed out. Please ensure the provided credentials and domain/URL are valid and try again.'
             )
           ),
         5000
@@ -113,11 +157,7 @@ export class TenableUtil {
             resolve(response.data.response.usable);
           })
           .catch((error) => {
-            if (error.response.data.error_code == 74) {
-              reject('Incorrect Access or Secret key');
-            } else {
-              reject(error.response.data.error_msg);
-            }
+            reject(`${error.name} : ${error.message}`);
           });
       } catch (e) {
         reject(e);
@@ -140,7 +180,7 @@ export class TenableUtil {
         () =>
           reject(
             new Error(
-              'Login timed out. Please check your CORS configuration or validate you have inputted the correct domain'
+              'Login timed out. Please check your CORS configuration and validate that the hostname is correct.'
             )
           ),
         5000
diff --git a/libs/interfaces/config/startup-settings.interface.ts b/libs/interfaces/config/startup-settings.interface.ts
index c304fadc0d..c9b7352a34 100644
--- a/libs/interfaces/config/startup-settings.interface.ts
+++ b/libs/interfaces/config/startup-settings.interface.ts
@@ -9,4 +9,6 @@ export interface IStartupSettings {
   readonly ldap: boolean;
   readonly registrationEnabled: boolean;
   readonly localLoginEnabled: boolean;
+  readonly tenableHostUrl: string;
+  readonly splunkHostUrl: string;
 }