CVE-2025-64996 is a vulnerability classified under CWE-732 (Incorrect Permission Assignment for Critical Resource) affecting Checkmk, a popular IT infrastructure monitoring software developed by Checkmk GmbH. The issue arises from 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 file system permissions—specifically, world-readable and writable. This misconfiguration allows any local user on the system, regardless of privilege level, to read the plugin's output files and manipulate them. Such unauthorized access can compromise the confidentiality and integrity of monitoring data, potentially misleading administrators or automated systems relying on accurate monitoring information. The vulnerability requires local access with low privileges but does not require user interaction or authentication beyond that. The CVSS 4.0 base score is 4.8 (medium severity), reflecting the limited attack vector (local) and the requirement for low privileges but no user interaction. The scope is limited to confidentiality and integrity impacts with no direct availability impact. No public exploits have been reported yet, but the vulnerability poses a risk especially in multi-user environments or where local access controls are weak. Since monitoring data is critical for operational awareness and incident response, tampering could delay detection of other attacks or cause misinformed operational decisions.

For European organizations, this vulnerability could lead to unauthorized disclosure and modification of monitoring data, undermining trust in IT infrastructure monitoring systems. This can result in delayed detection of security incidents, misconfiguration going unnoticed, or false alarms, impacting operational security and compliance with regulations such as NIS2 and GDPR. Organizations in sectors with stringent monitoring requirements—such as finance, healthcare, energy, and critical infrastructure—may face increased risk of insider threats or lateral movement by attackers who gain local access. The ability for low-privileged users to manipulate monitoring outputs could also facilitate privilege escalation or persistence by hiding malicious activity. Although the vulnerability does not directly impact availability, the indirect effects on incident response and system integrity can have significant operational consequences. European entities relying on Checkmk for centralized monitoring should consider this vulnerability a moderate risk that requires timely remediation to maintain security posture and regulatory compliance.

1. Upgrade Checkmk to versions 2.4.0p16, 2.3.0p41, or later, where the mk_inotify plugin permissions are correctly set. 2. Until patches are applied, restrict local user access to systems running Checkmk monitoring agents or servers to trusted personnel only. 3. Implement strict file system access controls and use mandatory access control (MAC) frameworks like SELinux or AppArmor to enforce least privilege on Checkmk plugin files. 4. Regularly audit file permissions and ownership of monitoring plugin outputs to detect any unauthorized changes. 5. Monitor local user activity and employ endpoint detection and response (EDR) solutions to detect suspicious file manipulations or privilege escalations. 6. Consider isolating monitoring infrastructure components on dedicated hosts with minimal user access. 7. Document and enforce policies for local user account management to reduce risk of unauthorized local access. 8. Review and enhance logging and alerting for changes to monitoring data files to enable rapid detection of tampering attempts.