SovBundle/Resources/assets/app/adminlte/form/form.scss

.form-sent {
  .form-control:invalid {
    border-color: #dc3545;
    padding-right: 2.25rem;
    background-image: url("data:image/svg+xml,%3csvg xmlns='http://www.w3.org/2000/svg' fill='%23dc3545' viewBox='-2 -2 7 7'%3e%3cpath stroke='%23dc3545' d='M0 0l3 3m0-3L0 3'/%3e%3ccircle r='.5'/%3e%3ccircle cx='3' r='.5'/%3e%3ccircle cy='3' r='.5'/%3e%3ccircle cx='3' cy='3' r='.5'/%3e%3c/svg%3E");
    background-repeat: no-repeat;
    background-position: center right calc(.375em + .1875rem);
    background-size: calc(.75em + .375rem) calc(.75em + .375rem);
  }

  select.form-control:invalid + .select2 .select2-selection {
    border-color: #dc3545;
  }

  select.form-control:invalid + .select2 .select2-selection b {
    border-color: #dc3545 transparent transparent transparent;
  }

  .form-check-label input:invalid ~ .checkmark {
    border-color: #dc3545;
  }
}

.nav-item .nav-link {
  position: relative;

  .invalid-form {
    display: none;
    position: absolute;
    top: -7px;
    right: -6px;
    color: #dc3545;
    background: #fff;
    border-radius: 10px;
    font-size: 1.2rem;
  }
}

.nav-item.has-invalid .nav-link .invalid-form {
  display: inline-block;
  z-index: 2;
}