CVE-2024-13723 is a vulnerability classified under CWE-434 (Unrestricted Upload of File with Dangerous Type) affecting the NagVis component within Checkmk, a popular IT monitoring solution. The flaw allows an attacker with authenticated administrative privileges to upload malicious PHP files without proper validation or restriction. By modifying specific settings within NagVis, the attacker can execute the uploaded PHP code remotely, resulting in remote code execution (RCE). This vulnerability affects NagVis version 1.9.40 and Checkmk version 2.3.0p2. The CVSS v3.1 base score is 7.2, indicating high severity, with attack vector being network-based, low attack complexity, requiring high privileges, no user interaction, and impacting confidentiality, integrity, and availability. The vulnerability is particularly dangerous because it allows an attacker to execute arbitrary code on the server hosting NagVis, potentially leading to full system compromise, data theft, or disruption of monitoring services. Although no exploits have been observed in the wild yet, the presence of administrative access prerequisites limits exploitation to insiders or attackers who have already breached initial defenses. The vulnerability stems from insufficient validation of uploaded files, allowing dangerous file types like PHP scripts to be uploaded and executed. This is a critical concern for organizations relying on Checkmk NagVis for monitoring, as it could undermine the integrity of their monitoring infrastructure and broader IT environment.

For European organizations, this vulnerability poses a significant threat to the security and reliability of IT monitoring infrastructure. Successful exploitation could lead to unauthorized system control, data breaches, and disruption of monitoring services, which are critical for maintaining operational continuity. Organizations in sectors such as finance, healthcare, energy, and government, which rely heavily on monitoring tools like Checkmk NagVis, could face operational downtime and regulatory repercussions under GDPR due to data confidentiality breaches. The requirement for administrative privileges reduces the risk from external attackers but raises concerns about insider threats or lateral movement after initial compromise. Additionally, compromised monitoring systems could be used as pivot points for further attacks within the network. The impact on availability could disrupt incident detection and response capabilities, increasing the window for attackers to operate undetected.

1. Apply official patches or updates from Checkmk as soon as they are released to address CVE-2024-13723. 2. Restrict administrative access to NagVis to trusted personnel only, enforcing strong authentication mechanisms such as multi-factor authentication (MFA). 3. Implement strict file upload controls and validation to prevent uploading of executable or dangerous file types, including disabling PHP execution in upload directories. 4. Conduct regular audits of uploaded files and configuration changes within NagVis to detect unauthorized modifications. 5. Employ network segmentation to isolate monitoring infrastructure from general user networks, limiting potential lateral movement. 6. Monitor logs for suspicious activities related to file uploads and administrative actions. 7. Educate administrators about the risks of this vulnerability and best practices for secure configuration. 8. Consider deploying web application firewalls (WAF) with rules to detect and block malicious file uploads targeting NagVis.