diff --git a/tests/behat/features/links.feature b/tests/behat/features/links.feature
index b622f2f10..8232ec01b 100644
--- a/tests/behat/features/links.feature
+++ b/tests/behat/features/links.feature
@@ -38,6 +38,10 @@ Feature: Content links processing
       | field_c_p_content:value  | <a href="http://exampleoverridden.com/external-dark-link">External dark link from overridden domain</a> |
       | field_c_p_content:format | civictheme_rich_text                                                                                    |
       | field_c_p_theme          | dark                                                                                                    |
+    And "field_c_n_components" in "civictheme_page" "node" with "title" of "[TEST] Page 1" has "civictheme_content" paragraph:
+      | field_c_p_content:value  | <a href="///C:/Users/civictheme/invalid">Invalid link</a> |
+      | field_c_p_content:format | civictheme_rich_text                                      |
+      | field_c_p_theme          | dark                                                      |
     And "field_c_n_components" in "civictheme_page" "node" with "title" of "[TEST] Page 1" has "civictheme_content" paragraph:
       | field_c_p_content:value  | <a href="tel:123412341234">Telephone link</a> |
       | field_c_p_content:format | civictheme_rich_text                          |
@@ -108,4 +112,9 @@ Feature: Content links processing
     And I should see an ".ct-basic-content a[href='http://exampleoverridden.com/external-dark-link'][target='_blank'].ct-content-link" element
     And I should not see an ".ct-basic-content a[href='http://exampleoverridden.com/external-dark-link'].ct-content-link.ct-content-link--external" element
 
+    And I should see an ".ct-basic-content a[href='///C:/Users/civictheme/invalid'].ct-content-link" element
+    And I should see an ".ct-basic-content a[href='///C:/Users/civictheme/invalid'].ct-theme-dark" element
+    And I should see an ".ct-basic-content a[href='///C:/Users/civictheme/invalid'][target='_blank'].ct-content-link" element
+    And I should not see an ".ct-basic-content a[href='///C:/Users/civictheme/invalid'].ct-content-link.ct-content-link--external" element
+
     And I should see an ".ct-basic-content a[href='mailto:person@test.com'].ct-content-link.ct-theme-dark" element
diff --git a/web/themes/contrib/civictheme/includes/utilities.inc b/web/themes/contrib/civictheme/includes/utilities.inc
index 79ab667f8..81e7aa3f2 100644
--- a/web/themes/contrib/civictheme/includes/utilities.inc
+++ b/web/themes/contrib/civictheme/includes/utilities.inc
@@ -653,33 +653,56 @@ function civictheme_get_icon_from_file(FileInterface $file): string {
  * @SuppressWarnings(PHPMD.StaticAccess)
  */
 function civictheme_url_is_external(string $url, string $base_url, array $override_domains = []): bool {
-  if (empty($url) || !UrlHelper::isValid($url)) {
+  if (!civictheme_url_is_valid($url)) {
     return FALSE;
   }
 
-  $url_parts = parse_url($url);
-  if (!empty($url_parts['scheme']) && empty($url_parts['host'])) {
+  if (!UrlHelper::isExternal($url)) {
     return FALSE;
   }
 
-  if (UrlHelper::isExternal($url)) {
-    $override_domains[] = $base_url;
-    foreach ($override_domains as $override_domain) {
-      $override_domain = civictheme_external_link_normalize_domain($override_domain);
+  $override_domains[] = $base_url;
+  foreach ($override_domains as $override_domain) {
+    $override_domain = civictheme_external_link_normalize_domain($override_domain);
 
-      if (!UrlHelper::isValid($override_domain, TRUE)) {
-        continue;
-      }
+    if (!civictheme_url_is_valid($override_domain, TRUE)) {
+      continue;
+    }
 
+    try {
       if (UrlHelper::externalIsLocal($url, $override_domain)) {
         return FALSE;
       }
     }
+    catch (\InvalidArgumentException $exception) {
+      return FALSE;
+    }
+  }
 
-    return TRUE;
+  return TRUE;
+}
+
+/**
+ * Check if a URL is valid.
+ *
+ * @param string $url
+ *   The URL to be checked.
+ * @param bool $absolute
+ *   Whether the URL is absolute (beginning with a scheme such as "http:").
+ *
+ * @return bool
+ *   TRUE if the provided URL is valid.
+ *
+ * @SuppressWarnings(PHPMD.StaticAccess)
+ * @SuppressWarnings(PHPMD.BooleanArgumentFlag)
+ */
+function civictheme_url_is_valid(string $url, bool $absolute = FALSE) : bool {
+  if (empty($url) || !UrlHelper::isValid($url, $absolute)) {
+    return FALSE;
   }
 
-  return FALSE;
+  $url_parts = parse_url($url);
+  return !(!empty($url_parts['scheme']) && empty($url_parts['host']));
 }
 
 /**