CVE-2025-64996 is a vulnerability identified in Checkmk, a widely used IT infrastructure monitoring solution developed by Checkmk GmbH. The flaw resides in the mk_inotify plugin, which in affected versions (prior to 2.4.0p16, 2.3.0p41, and all 2.2.0 and older) creates files with overly permissive access controls—specifically, world-readable and writable permissions. This incorrect permission assignment (classified as CWE-732) allows any local user on the system to read the plugin's output files and modify them arbitrarily. Since these files contain monitoring data, unauthorized users can potentially manipulate monitoring results, leading to false alerts, suppression of critical notifications, or unauthorized disclosure of sensitive monitoring information. The vulnerability requires only local access with low privileges (local attacker with limited rights), no user interaction, and no elevated privileges, making it relatively easy to exploit in environments where multiple users have local system access. The CVSS v4.0 score of 4.8 (medium severity) reflects the limited attack vector (local), low complexity, and partial impact on confidentiality and integrity, but no impact on availability or authentication requirements. No public exploits or active exploitation have been reported to date. The vulnerability affects multiple major versions of Checkmk, emphasizing the need for patching or configuration changes. Since Checkmk is often deployed in enterprise and critical infrastructure environments for monitoring, the integrity and confidentiality of monitoring data are crucial for operational security and incident response.

For European organizations, this vulnerability poses a risk primarily in multi-user environments where local access to monitoring servers is possible, such as shared hosting, managed service providers, or large enterprises with multiple administrators. Unauthorized modification of monitoring data can lead to undetected system failures, delayed incident response, or false security alerts, potentially causing operational disruptions or security blind spots. Confidentiality breaches could expose sensitive infrastructure details. In critical infrastructure sectors (energy, transportation, finance), such manipulation could have cascading effects on service availability and safety. The medium severity and local access requirement limit the threat to insider attackers or compromised accounts with local access, but the impact on trustworthiness of monitoring data is significant. Organizations relying heavily on Checkmk for real-time monitoring and alerting must consider this vulnerability a risk to their security posture and operational continuity.

1. Upgrade Checkmk to the latest patched versions: 2.4.0p16 or 2.3.0p41 and above, where this issue is resolved. 2. If immediate patching is not possible, manually audit and restrict file permissions for mk_inotify plugin output files to prevent world-readable and writable access. Use chmod to set permissions to owner-only or group-restricted access. 3. Limit local user access to monitoring servers strictly to trusted administrators and use hardened user account policies. 4. Monitor file system changes and audit logs for unauthorized modifications to monitoring plugin files. 5. Employ host-based intrusion detection systems (HIDS) to detect anomalous file permission changes or tampering attempts. 6. Review and enforce least privilege principles for all local users on monitoring hosts. 7. Regularly verify integrity of monitoring data and cross-check alerts with alternative sources to detect manipulation. 8. Incorporate this vulnerability into organizational risk assessments and incident response plans to prepare for potential exploitation scenarios.