diff --git a/src/Api/AdminConsole/Controllers/OrganizationUsersController.cs b/src/Api/AdminConsole/Controllers/OrganizationUsersController.cs
index 37b58bc252..081a86c9ad 100644
--- a/src/Api/AdminConsole/Controllers/OrganizationUsersController.cs
+++ b/src/Api/AdminConsole/Controllers/OrganizationUsersController.cs
@@ -324,6 +324,12 @@ public class OrganizationUsersController : BaseAdminConsoleController
             throw new UnauthorizedAccessException();
         }
 
+        var organizationUser = await _organizationUserRepository.GetByIdAsync(organizationUserId);
+        if (organizationUser == null || organizationUser.OrganizationId != orgId)
+        {
+            throw new NotFoundException("Organization user mismatch");
+        }
+
         var useMasterPasswordPolicy = _featureService.IsEnabled(FeatureFlagKeys.PolicyRequirements)
         ? (await _policyRequirementQuery.GetAsync<ResetPasswordPolicyRequirement>(user.Id)).AutoEnrollEnabled(orgId)
         : await ShouldHandleResetPasswordAsync(orgId);
diff --git a/test/Api.Test/AdminConsole/Controllers/OrganizationUsersControllerTests.cs b/test/Api.Test/AdminConsole/Controllers/OrganizationUsersControllerTests.cs
index 68a63bf579..7edd3c662c 100644
--- a/test/Api.Test/AdminConsole/Controllers/OrganizationUsersControllerTests.cs
+++ b/test/Api.Test/AdminConsole/Controllers/OrganizationUsersControllerTests.cs
@@ -121,10 +121,37 @@ public class OrganizationUsersControllerTests
 
     [Theory]
     [BitAutoData]
-    public async Task Accept_NoMasterPasswordReset(Guid orgId, Guid orgUserId,
-        OrganizationUserAcceptRequestModel model, User user, SutProvider<OrganizationUsersController> sutProvider)
+    public async Task Accept_WhenOrganizationUserNotFound_ThrowsNotFoundException(
+        Guid orgId, Guid orgUserId, OrganizationUserAcceptRequestModel model, User user,
+        SutProvider<OrganizationUsersController> sutProvider)
     {
         sutProvider.GetDependency<IUserService>().GetUserByPrincipalAsync(default).ReturnsForAnyArgs(user);
+        sutProvider.GetDependency<IOrganizationUserRepository>().GetByIdAsync(orgUserId).Returns((OrganizationUser)null);
+
+        await Assert.ThrowsAsync<NotFoundException>(() => sutProvider.Sut.Accept(orgId, orgUserId, model));
+    }
+
+    [Theory]
+    [BitAutoData]
+    public async Task Accept_WhenOrganizationIdMismatch_ThrowsNotFoundException(
+        Guid orgId, Guid orgUserId, OrganizationUserAcceptRequestModel model, User user, OrganizationUser organizationUser,
+        SutProvider<OrganizationUsersController> sutProvider)
+    {
+        organizationUser.OrganizationId = Guid.NewGuid(); // Different org ID
+        sutProvider.GetDependency<IUserService>().GetUserByPrincipalAsync(default).ReturnsForAnyArgs(user);
+        sutProvider.GetDependency<IOrganizationUserRepository>().GetByIdAsync(orgUserId).Returns(organizationUser);
+
+        await Assert.ThrowsAsync<NotFoundException>(() => sutProvider.Sut.Accept(orgId, orgUserId, model));
+    }
+
+    [Theory]
+    [BitAutoData]
+    public async Task Accept_NoMasterPasswordReset(Guid orgId, Guid orgUserId,
+        OrganizationUserAcceptRequestModel model, User user, OrganizationUser organizationUser, SutProvider<OrganizationUsersController> sutProvider)
+    {
+        organizationUser.OrganizationId = orgId;
+        sutProvider.GetDependency<IUserService>().GetUserByPrincipalAsync(default).ReturnsForAnyArgs(user);
+        sutProvider.GetDependency<IOrganizationUserRepository>().GetByIdAsync(orgUserId).Returns(organizationUser);
 
         await sutProvider.Sut.Accept(orgId, orgUserId, model);
 
@@ -137,17 +164,19 @@ public class OrganizationUsersControllerTests
     [Theory]
     [BitAutoData]
     public async Task Accept_WhenOrganizationUsePoliciesIsEnabledAndResetPolicyIsEnabled_ShouldHandleResetPassword(Guid orgId, Guid orgUserId,
-        OrganizationUserAcceptRequestModel model, User user,
+        OrganizationUserAcceptRequestModel model, User user, OrganizationUser organizationUser,
         [Policy(PolicyType.ResetPassword, true)] PolicyStatus policy,
         SutProvider<OrganizationUsersController> sutProvider)
     {
         // Arrange
+        organizationUser.OrganizationId = orgId;
         var applicationCacheService = sutProvider.GetDependency<IApplicationCacheService>();
         applicationCacheService.GetOrganizationAbilityAsync(orgId).Returns(new OrganizationAbility { UsePolicies = true });
 
         policy.Data = CoreHelpers.ClassToJsonData(new ResetPasswordDataModel { AutoEnrollEnabled = true, });
         var userService = sutProvider.GetDependency<IUserService>();
         userService.GetUserByPrincipalAsync(default).ReturnsForAnyArgs(user);
+        sutProvider.GetDependency<IOrganizationUserRepository>().GetByIdAsync(orgUserId).Returns(organizationUser);
 
         var policyQuery = sutProvider.GetDependency<IPolicyQuery>();
         policyQuery.RunAsync(orgId,
@@ -171,17 +200,19 @@ public class OrganizationUsersControllerTests
     [Theory]
     [BitAutoData]
     public async Task Accept_WhenOrganizationUsePoliciesIsDisabled_ShouldNotHandleResetPassword(Guid orgId, Guid orgUserId,
-        OrganizationUserAcceptRequestModel model, User user,
+        OrganizationUserAcceptRequestModel model, User user, OrganizationUser organizationUser,
         [Policy(PolicyType.ResetPassword, true)] PolicyStatus policy,
         SutProvider<OrganizationUsersController> sutProvider)
     {
         // Arrange
+        organizationUser.OrganizationId = orgId;
         var applicationCacheService = sutProvider.GetDependency<IApplicationCacheService>();
         applicationCacheService.GetOrganizationAbilityAsync(orgId).Returns(new OrganizationAbility { UsePolicies = false });
 
         policy.Data = CoreHelpers.ClassToJsonData(new ResetPasswordDataModel { AutoEnrollEnabled = true, });
         var userService = sutProvider.GetDependency<IUserService>();
         userService.GetUserByPrincipalAsync(default).ReturnsForAnyArgs(user);
+        sutProvider.GetDependency<IOrganizationUserRepository>().GetByIdAsync(orgUserId).Returns(organizationUser);
 
         var policyQuery = sutProvider.GetDependency<IPolicyQuery>();
         policyQuery.RunAsync(orgId,
@@ -360,13 +391,15 @@ public class OrganizationUsersControllerTests
     [Theory]
     [BitAutoData]
     public async Task Accept_WhenOrganizationUsePoliciesIsEnabledAndResetPolicyIsEnabled_WithPolicyRequirementsEnabled_ShouldHandleResetPassword(Guid orgId, Guid orgUserId,
-        OrganizationUserAcceptRequestModel model, User user, SutProvider<OrganizationUsersController> sutProvider)
+        OrganizationUserAcceptRequestModel model, User user, OrganizationUser organizationUser, SutProvider<OrganizationUsersController> sutProvider)
     {
         // Arrange
+        organizationUser.OrganizationId = orgId;
         var applicationCacheService = sutProvider.GetDependency<IApplicationCacheService>();
         applicationCacheService.GetOrganizationAbilityAsync(orgId).Returns(new OrganizationAbility { UsePolicies = true });
 
         sutProvider.GetDependency<IFeatureService>().IsEnabled(FeatureFlagKeys.PolicyRequirements).Returns(true);
+        sutProvider.GetDependency<IOrganizationUserRepository>().GetByIdAsync(orgUserId).Returns(organizationUser);
 
         var policy = new Policy
         {
@@ -403,14 +436,16 @@ public class OrganizationUsersControllerTests
     [Theory]
     [BitAutoData]
     public async Task Accept_WithInvalidModelResetPasswordKey_WithPolicyRequirementsEnabled_ThrowsBadRequestException(Guid orgId, Guid orgUserId,
-        OrganizationUserAcceptRequestModel model, User user, SutProvider<OrganizationUsersController> sutProvider)
+        OrganizationUserAcceptRequestModel model, User user, OrganizationUser organizationUser, SutProvider<OrganizationUsersController> sutProvider)
     {
         // Arrange
         model.ResetPasswordKey = " ";
+        organizationUser.OrganizationId = orgId;
         var applicationCacheService = sutProvider.GetDependency<IApplicationCacheService>();
         applicationCacheService.GetOrganizationAbilityAsync(orgId).Returns(new OrganizationAbility { UsePolicies = true });
 
         sutProvider.GetDependency<IFeatureService>().IsEnabled(FeatureFlagKeys.PolicyRequirements).Returns(true);
+        sutProvider.GetDependency<IOrganizationUserRepository>().GetByIdAsync(orgUserId).Returns(organizationUser);
 
         var policy = new Policy
         {