CVE-2026-24097: Observable Response Discrepancy

Improper permission enforcement in Checkmk versions 2.4.0 before 2.4.0p23, 2.3.0 before 2.3.0p43, and 2.2.0 EOL allows authenticated users to enumerate existing hosts by observing different HTTP response codes in agent-receiver/registerexisting endpoint, which could lead to information disclosure...