<div class="cp_card">
コンテンツ
  <div class="cp_ribbon09">
    <div class="cp_ribbon">Ribbon</div>
  </div>
</div>

.cp_card {
  position: relative;/*リボンをかけたいコンテンツボックスにセット*/
  width: 300px;
  height: 300px;
  background: #ffffff;
  margin: auto;
  padding: 5px;
  box-shadow: 0 0 5px rgba(0, 0, 0, 0.3);
}
/*リボンの位置*/
.cp_ribbon09 {
  position: absolute;
  top: 15px;
  right: -6px;
  display: flex;
  align-items: center;
  height: 40px;
  padding: 0 10px;
  color: #ffffff;
  background: #21759a;
}
.cp_ribbon09:before,
.cp_ribbon09:after {
  position: absolute;
  content: '';
}
.cp_ribbon09:before {
  top: -6px;
  right: 0;
  border-top: 3px solid transparent;
  border-right: 3px solid transparent;
  border-bottom: 3px solid #14455b;
  border-left: 3px solid #14455b;
}
.cp_ribbon09:after {
  top: 0;
  left: -20px;
  border-top: 20px solid #21759a;
  border-bottom: 20px solid #21759a;
  border-left: 20px solid transparent;
}