D8 generate double URL for commerce product
In your hook_entity_update() do like below

    function mymodule_entity_update(Drupal\Core\Entity\EntityInterface $entity) {
      if($entity-&gt;getEntityTypeId() == 'commerce_product'){
        $language = \Drupal::languageManager()-&gt;getCurrentLanguage()-&gt;getId();
        $aliasStorage = \Drupal::service('path.alias_storage');
        $source = '/product/' . $entity-&gt;id();
        if ($aliasStorage-&gt;aliasExists($source, $langcode)) {
          // alias already exist. So save your second alias here.
          $aliasStorage-&gt;save('/product/' . $entity-&gt;id(), YOURNEWALIAS, $language);

        }
        else {
           $aliasStorage-&gt;save('/product/' . $entity-&gt;id(), YOURNEWALIAS_1, $language);
           $aliasStorage-&gt;save('/product/' . $entity-&gt;id(), YOURNEWALIAS_2, $language);
        }
        }
    }