CVE-2024-23985 is a high-severity denial of service (DoS) vulnerability affecting EzServer version 6.4.017. The vulnerability is triggered when the server processes an excessively long string input, specifically noted with the RNTO command, which is part of the FTP protocol used for renaming files. This malformed input causes the EzServer daemon to crash, resulting in a denial of service condition. The vulnerability has a CVSS v3.1 base score of 7.5, reflecting its high impact on availability with no required privileges, no user interaction, and remote network attack vector. The vulnerability does not impact confidentiality or integrity but solely affects availability by crashing the server process. No vendor or product details beyond EzServer 6.4.017 are provided, and no patches or known exploits in the wild have been reported as of the publication date (January 25, 2024). The lack of authentication or user interaction requirements means an attacker can remotely exploit this vulnerability to disrupt services by sending a crafted RNTO command with a long string, causing the server to become unresponsive or crash. This could lead to service outages, impacting business continuity and potentially causing operational disruption for organizations relying on EzServer for FTP services.

For European organizations using EzServer 6.4.017, this vulnerability poses a significant risk to service availability. FTP servers are often used for file transfers in various industries including manufacturing, logistics, and IT services. A successful DoS attack could disrupt critical file transfer operations, delay business processes, and cause downtime. This is particularly impactful for organizations with automated workflows dependent on FTP transfers. Additionally, prolonged or repeated crashes could lead to reputational damage and increased operational costs due to recovery efforts. Since the vulnerability can be exploited remotely without authentication, attackers can cause disruption without needing insider access, increasing the threat surface. Organizations in sectors with stringent uptime requirements, such as finance, healthcare, and public services, may face compliance and regulatory challenges if service availability is compromised.

To mitigate this vulnerability, organizations should first verify if they are running EzServer 6.4.017 or any affected versions. Since no official patch or vendor information is currently available, immediate mitigation steps include implementing network-level protections such as firewall rules to restrict or monitor FTP traffic, especially commands like RNTO. Deploying intrusion detection/prevention systems (IDS/IPS) with signatures or anomaly detection for unusually long RNTO commands can help block exploit attempts. Network segmentation to isolate FTP servers from critical infrastructure reduces potential impact. Administrators should also consider disabling or limiting FTP services if not essential or migrating to more secure file transfer protocols (e.g., SFTP or FTPS) that provide better security controls. Monitoring server logs for abnormal command lengths and crashes can provide early warning signs. Once a vendor patch or update is released, prompt application is critical. Additionally, maintaining regular backups and having incident response plans for DoS scenarios will improve resilience.