CVE-2025-64999: Checkmk

Medium severity, CVSS 5.4. EPSS: 0.1% chance of exploitation in the next 30 days.

Improper neutralization of input in Checkmk versions 2.4.0 before 2.4.0p22, and 2.3.0 before 2.3.0p43 allows an attacker that can manipulate a host's check output to inject malicious JavaScript into the Synthetic Monitoring HTML logs, which can then be accessed via a crafted phishing link.

Affected products

• Checkmk Checkmk: version 2.3.0 only; version 2.4.0 only

Published 2026-02-26. Last modified 2026-06-17.