diff --git a/framework/src/Volo.Abp.AspNetCore.MultiTenancy/Volo/Abp/AspNetCore/MultiTenancy/MultiTenancyMiddleware.cs b/framework/src/Volo.Abp.AspNetCore.MultiTenancy/Volo/Abp/AspNetCore/MultiTenancy/MultiTenancyMiddleware.cs
index 8fc6a3995c..00b3f87056 100644
--- a/framework/src/Volo.Abp.AspNetCore.MultiTenancy/Volo/Abp/AspNetCore/MultiTenancy/MultiTenancyMiddleware.cs
+++ b/framework/src/Volo.Abp.AspNetCore.MultiTenancy/Volo/Abp/AspNetCore/MultiTenancy/MultiTenancyMiddleware.cs
@@ -118,6 +118,12 @@ public class MultiTenancyMiddleware : IMiddleware, ITransientDependency
             uiCulture = defaultLanguage;
         }
 
-        return new RequestCulture(culture, uiCulture);
+        if (CultureHelper.IsValidCultureCode(culture) &&
+            CultureHelper.IsValidCultureCode(uiCulture))
+        {
+            return new RequestCulture(culture, uiCulture);
+        }
+
+        return null;
     }
 }
diff --git a/framework/src/Volo.Abp.AspNetCore.Mvc/Volo/Abp/AspNetCore/Mvc/Localization/AbpLanguagesController.cs b/framework/src/Volo.Abp.AspNetCore.Mvc/Volo/Abp/AspNetCore/Mvc/Localization/AbpLanguagesController.cs
index 9f5d6aa530..8a4f82953a 100644
--- a/framework/src/Volo.Abp.AspNetCore.Mvc/Volo/Abp/AspNetCore/Mvc/Localization/AbpLanguagesController.cs
+++ b/framework/src/Volo.Abp.AspNetCore.Mvc/Volo/Abp/AspNetCore/Mvc/Localization/AbpLanguagesController.cs
@@ -1,6 +1,7 @@
 using Microsoft.AspNetCore.Localization;
 using Microsoft.AspNetCore.Mvc;
 using System;
+using System.Globalization;
 using System.Threading.Tasks;
 using Microsoft.AspNetCore.RequestLocalization;
 using Volo.Abp.Auditing;
@@ -30,6 +31,11 @@ public class AbpLanguagesController : AbpController
             throw new AbpException("The selected culture is not valid! Make sure you enter a valid culture code.");
         }
 
+        if (!CultureHelper.IsValidCultureCode(uiCulture))
+        {
+            throw new AbpException("The selected uiCulture is not valid! Make sure you enter a valid culture code.");
+        }
+
         AbpRequestCultureCookieHelper.SetCultureCookie(
             HttpContext,
             new RequestCulture(culture, uiCulture)
diff --git a/framework/src/Volo.Abp.Core/Volo/Abp/Localization/CultureHelper.cs b/framework/src/Volo.Abp.Core/Volo/Abp/Localization/CultureHelper.cs
index 74a62116a4..adf2890b21 100644
--- a/framework/src/Volo.Abp.Core/Volo/Abp/Localization/CultureHelper.cs
+++ b/framework/src/Volo.Abp.Core/Volo/Abp/Localization/CultureHelper.cs
@@ -47,7 +47,7 @@ public static class CultureHelper
 
         try
         {
-            CultureInfo.GetCultureInfo(cultureCode);
+            _ = CultureInfo.GetCultureInfo(cultureCode);
             return true;
         }
         catch (CultureNotFoundException)