CVE-2024-40457 identifies a critical security vulnerability in the No-IP Dynamic Update Client (DUC) version 3.x, where user credentials are stored and transmitted in cleartext. This includes exposure on command lines and within configuration files such as /etc/default/noip-duc. The vendor explicitly recommends this practice, which is unusual and increases the risk of credential compromise. The vulnerability is classified under CWE-312 (Cleartext Storage of Sensitive Information). The CVSS v3.1 score is 9.1, reflecting its critical severity due to network attack vector (AV:N), low attack complexity (AC:L), no privileges required (PR:N), no user interaction (UI:N), and high impact on confidentiality (C:H) and availability (A:H), though integrity is not impacted (I:N). Attackers can intercept or access these credentials easily, enabling unauthorized dynamic DNS updates, potentially redirecting traffic, causing denial of service, or facilitating further attacks. No patches or mitigations are currently provided by the vendor, and no exploits are known in the wild yet. This vulnerability affects all deployments of No-IP DUC v3.x where default configurations are used, especially on Linux systems where /etc/default/noip-duc is common.

The primary impact of CVE-2024-40457 is the compromise of confidentiality and availability. Attackers gaining access to cleartext credentials can hijack dynamic DNS updates, redirecting legitimate traffic to malicious servers or causing service outages. This can disrupt business operations, degrade user trust, and facilitate man-in-the-middle attacks or further network intrusions. Since no authentication or user interaction is required, exploitation can be automated and widespread. Organizations relying on No-IP DUC for critical infrastructure or service continuity face significant operational risks. The exposure of credentials on command lines or files also increases insider threat risks and accidental leaks through logs or backups. The absence of vendor patches means the vulnerability may persist for extended periods, increasing the window of opportunity for attackers.

Given the vendor's intentional design choice to store credentials in cleartext, organizations must implement compensating controls. First, restrict access permissions on configuration files like /etc/default/noip-duc to the minimum necessary users (e.g., root only) to reduce exposure. Use operating system-level auditing and monitoring to detect unauthorized access to these files or command-line invocations containing credentials. Consider isolating the No-IP DUC client in a hardened environment or container to limit lateral movement if compromised. Employ network segmentation and firewall rules to restrict dynamic DNS update traffic to trusted sources only. Where possible, replace or supplement No-IP DUC with alternative dynamic DNS clients that support encrypted credential storage or token-based authentication. Regularly review and rotate credentials used by the client to limit the impact of potential leaks. Finally, educate system administrators about the risks of cleartext credentials and enforce secure operational procedures to avoid accidental exposure through logs or shared scripts.