HTTP request/response smuggling vulnerability in HAProxy version 2.7.0, and 2.6.1 to 2.6.7 allows a remote attacker to alter a legitimate user's request. As a result, the attacker may obtain sensitive information or cause a denial-of-service (DoS) condition.
https://jvn.jp/en/jp/JVN38170084/
https://git.haproxy.org/?p=haproxy-2.7.git%3Ba=commit%3Bh=3ca4223c5e1f18a19dc93b0b09ffdbd295554d46