The "NagVis" component within Checkmk is vulnerable to remote code execution. An authenticated attacker with administrative level privileges is able to upload a malicious PHP file and modify specific settings to execute the contents of the file as PHP.
https://www.nagvis.org/downloads/changelog/1.9.42
https://korelogic.com/Resources/Advisories/KL-001-2025-002.txt
https://checkmk.com/werks?version=2.3.0p10