Icinga is a monitoring system which checks the availability of network resources, notifies users of outages, and generates performance data for reporting. The TLS certificate validation in all Icinga 2 versions starting from 2.4.0 was flawed, allowing an attacker to impersonate both trusted cluster nodes as well as any API users that use TLS client certificates for authentication (ApiUser objects with the client_cn attribute set). This vulnerability has been fixed in v2.14.3, v2.13.10, v2.12.11, and v2.11.12.
https://icinga.com/blog/2024/11/12/critical-icinga-2-security-releases-2-14-3
https://github.com/Icinga/icinga2/security/advisories/GHSA-j7wq-r9mg-9wpv
https://github.com/Icinga/icinga2/commit/8fed6608912c752b337d977f730547875a820831
https://github.com/Icinga/icinga2/commit/869a7d6f0fe38c748e67bacc1fbdd42c933030f6
https://github.com/Icinga/icinga2/commit/3504fc7ed688c10d86988e2029a65efc311393fe
https://github.com/Icinga/icinga2/commit/2febc5e18ae0c93d989e64ebc2a9fd90e7205ad8
https://github.com/Icinga/icinga2/commit/0419a2c36de408e9a703aec0962061ec9a285d3c