Improper certificate validation in Logstash's TCP output could lead to a man-in-the-middle (MitM) attack in “client” mode, as hostname verification in TCP output was not being performed when the ssl_verification_mode => full was set.
https://discuss.elastic.co/t/logstash-8-17-6-8-18-1-and-9-0-1-security-update-esa-2025-08/377869