Icinga 2 is an open source monitoring system. From 2.8 until 2.14.9, 2.15.4, and 2.16.2, certificate update JSON-RPC message handling does not validate that the sender is a trusted endpoint. An unauthenticated network attacker able to connect to TCP port 5665 can replace the node certificate and trusted CA certificate, impersonate a trusted node, and take control of the node. This issue is fixed in versions 2.14.9, 2.15.4, and 2.16.2.
https://icinga.com/blog/icinga2-security-release-v2-16-2
https://github.com/Icinga/icinga2/security/advisories/GHSA-vj39-ww8j-vvx5
https://github.com/Icinga/icinga2/releases/tag/v2.16.2
https://github.com/Icinga/icinga2/releases/tag/v2.15.4
https://github.com/Icinga/icinga2/releases/tag/v2.14.9
https://github.com/Icinga/icinga2/pull/10907
https://github.com/Icinga/icinga2/commit/d37b0cfd7d9595ae2f02fadb3d724c98d8620f81
https://github.com/Icinga/icinga2/commit/a6f7cc7a4ef8beed023b24416106822d6940c4c0
https://github.com/Icinga/icinga2/commit/6c2e0db3819f859910a4ae265461cb51b1d2039c
https://github.com/Icinga/icinga2/commit/4b7fb3405f4616a24b2b55e20f603a56b7dd6ad0