CVE-2026-2859: Checkmk

Medium severity, CVSS 4.3. EPSS: 0.3% chance of exploitation in the next 30 days.

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 unauthenticated users to enumerate existing hosts by observing different HTTP response codes in deploy_agent endpoint, which could lead to information disclosure.

Affected products

• Checkmk Checkmk: version 2.2.0 only; version 2.3.0 only; version 2.4.0 only

Published 2026-03-13. Last modified 2026-06-17.