The vulnerability CVE-2024-39917 affects neutrinolabs xrdp, an open-source Remote Desktop Protocol (RDP) server widely used on Linux systems. Versions up to and including 0.10.0 fail to enforce the configured maximum login attempts parameter, MaxLoginRetry, located in /etc/xrdp/sesman.ini. This misconfiguration or implementation flaw allows attackers to attempt an unlimited number of authentication attempts without being blocked or throttled. The vulnerability is classified under CWE-307, which concerns improper restriction of excessive authentication attempts. Exploiting this flaw requires no authentication or user interaction and can be performed remotely over the network. The primary risk is that attackers can conduct brute-force password guessing attacks indefinitely, increasing the likelihood of credential compromise. Additionally, the unlimited login attempts can be leveraged to cause denial of service by overwhelming the authentication subsystem or locking out legitimate users through account lockout policies if implemented externally. The CVSS v3.1 base score of 7.2 reflects a high severity due to network accessibility, low attack complexity, no privileges or user interaction needed, and a scope change where confidentiality is partially impacted and availability is degraded. Although no known exploits are reported in the wild at the time of publication, the vulnerability presents a significant risk to any organization exposing xrdp services, especially those with weak or reused credentials. The lack of an effective login attempt limit undermines a fundamental security control designed to prevent brute-force attacks, making this a critical issue for administrators to address promptly.

For European organizations, the impact of CVE-2024-39917 can be substantial. Many enterprises and public sector entities in Europe use Linux-based systems with xrdp to provide remote desktop access, especially in hybrid and remote work environments. The vulnerability enables attackers to perform unlimited brute-force attempts, increasing the risk of credential compromise and unauthorized access to sensitive systems. This can lead to data breaches, lateral movement within networks, and potential disruption of critical services. The partial confidentiality impact means that attackers may gain access to user accounts or sensitive information if credentials are cracked. The availability impact could manifest as denial of service if authentication services are overwhelmed or accounts are locked out. Given the regulatory environment in Europe, including GDPR, unauthorized access and data breaches could result in significant legal and financial penalties. Organizations in sectors such as finance, healthcare, government, and critical infrastructure are particularly at risk due to the sensitive nature of their data and services. The vulnerability also poses a risk to managed service providers and cloud environments that use xrdp for remote management. Without mitigation, attackers could exploit this flaw to gain persistent footholds or disrupt operations.

To mitigate CVE-2024-39917, European organizations should take the following specific actions: 1) Upgrade xrdp to a version later than 0.10.0 once an official patch addressing this vulnerability is released by neutrinolabs. 2) Until a patch is available, implement external rate-limiting controls on the network perimeter or host-based firewalls to restrict the number of authentication attempts from a single IP address. 3) Deploy intrusion detection and prevention systems (IDS/IPS) with signatures or heuristics to detect and block brute-force login attempts against xrdp services. 4) Enforce strong password policies and multi-factor authentication (MFA) for all remote desktop access to reduce the risk of credential compromise. 5) Monitor authentication logs closely for unusual login patterns or repeated failed attempts and respond promptly to suspicious activity. 6) Consider isolating xrdp services behind VPNs or zero-trust network access (ZTNA) solutions to limit exposure to the public internet. 7) Regularly audit and update configuration files, ensuring MaxLoginRetry and other security parameters are correctly set and effective. 8) Educate system administrators and users about the risks of brute-force attacks and the importance of secure remote access practices. These measures collectively reduce the attack surface and improve detection and response capabilities.