CVE-2021-46854 is a high-severity vulnerability affecting the mod_radius module in ProFTPD versions prior to 1.3.7c. ProFTPD is a widely used FTP server software, and mod_radius is a module that integrates RADIUS authentication for user access control. The vulnerability arises because mod_radius copies blocks of 16 characters without proper bounds checking, leading to a memory disclosure issue. Specifically, this flaw allows an unauthenticated remote attacker to send crafted RADIUS requests that cause the server to leak memory contents. The vulnerability does not require any authentication or user interaction, and it can be exploited remotely over the network (AV:N). The attack complexity is low (AC:L), meaning exploitation is straightforward. The vulnerability impacts confidentiality (C:H) by potentially exposing sensitive memory data, but it does not affect integrity or availability (I:N, A:N). Although no known exploits are currently reported in the wild, the presence of this vulnerability in a critical authentication module poses a significant risk. The vulnerability is classified under CWE-401, which relates to improper handling of memory leading to information disclosure. Since ProFTPD is commonly deployed on Unix-like systems for FTP services, organizations using this software with mod_radius enabled are at risk of sensitive data leakage, including authentication credentials or other memory-resident information. The lack of a patch link suggests that users should verify they are running version 1.3.7c or later, where this issue is addressed.

For European organizations, the impact of this vulnerability can be substantial, especially for those relying on ProFTPD with mod_radius for FTP services and RADIUS-based authentication. Confidential information such as user credentials, session tokens, or other sensitive data stored in memory could be exposed to remote attackers, leading to unauthorized access or further compromise. This is particularly critical for sectors handling sensitive data, including finance, healthcare, government, and critical infrastructure. The vulnerability's remote exploitability without authentication increases the attack surface, potentially allowing attackers to gather intelligence or prepare for more targeted attacks. Additionally, organizations with compliance obligations under GDPR may face regulatory and reputational consequences if data leakage occurs. While the vulnerability does not directly impact system integrity or availability, the confidentiality breach alone can facilitate lateral movement or privilege escalation in a broader attack chain.

1. Immediate upgrade to ProFTPD version 1.3.7c or later, where the vulnerability is fixed. 2. If upgrading is not immediately feasible, disable the mod_radius module to eliminate the attack vector. 3. Restrict network access to the RADIUS server and FTP services using firewall rules, allowing only trusted IP addresses to communicate. 4. Monitor network traffic for unusual RADIUS requests or anomalies that could indicate exploitation attempts. 5. Conduct memory and log analysis to detect any signs of information leakage or suspicious activity. 6. Implement network segmentation to isolate FTP servers from critical internal systems. 7. Review and tighten RADIUS server configurations to minimize exposure. 8. Employ intrusion detection/prevention systems (IDS/IPS) with signatures or heuristics targeting anomalous RADIUS traffic. 9. Educate system administrators about the vulnerability and ensure timely application of security patches in the future.