CVE-2025-21349 is a vulnerability classified under CWE-287 (Improper Authentication) affecting the Windows Remote Desktop Configuration Service on Microsoft Windows 10 Version 1809 (build 10.0.17763.0). This flaw allows an unauthenticated remote attacker to tamper with Remote Desktop configuration settings by bypassing authentication mechanisms that should protect these configurations. The vulnerability arises because the service does not properly enforce authentication checks before allowing configuration changes, potentially enabling attackers to alter Remote Desktop settings such as enabling unauthorized remote access or modifying security parameters. The CVSS 3.1 base score is 6.8, indicating a medium severity level, with the vector indicating network attack vector (AV:N), high attack complexity (AC:H), no privileges required (PR:N), user interaction required (UI:R), unchanged scope (S:U), and high impact on confidentiality and integrity (C:H/I:H) but no impact on availability (A:N). Exploitation requires the attacker to have network access to the affected service and trick a user into interaction, such as clicking a malicious link or opening a crafted file, but does not require prior authentication or elevated privileges. No known exploits have been reported in the wild as of the publication date. The vulnerability was reserved in December 2024 and published in February 2025. The absence of patch links suggests that a fix may not yet be publicly available, emphasizing the need for mitigation through other controls. This vulnerability is significant because Remote Desktop services are commonly used for remote administration and access, and improper authentication could lead to unauthorized access or configuration changes that compromise system security and data confidentiality.

For European organizations, this vulnerability poses a risk of unauthorized access to Remote Desktop configurations, potentially allowing attackers to enable or manipulate remote access settings without proper authorization. This could lead to exposure of sensitive data, unauthorized lateral movement within networks, and compromise of critical systems. Organizations relying on Windows 10 Version 1809, especially those in sectors with high remote administration usage such as finance, healthcare, and government, may face increased risk. The medium severity score reflects that while exploitation is not trivial due to high attack complexity and user interaction requirements, the impact on confidentiality and integrity is high. This could result in data breaches, loss of trust, and operational disruptions. Additionally, the lack of a current patch increases exposure time. European entities with legacy systems or slow patch cycles are particularly vulnerable. The threat is amplified in environments where Remote Desktop services are exposed to untrusted networks or the internet without adequate network segmentation or access controls.

1. Upgrade affected systems to a supported and patched version of Windows 10 or later where this vulnerability is resolved. 2. Restrict network access to Remote Desktop services using firewalls, VPNs, or network segmentation to limit exposure to trusted users only. 3. Disable Remote Desktop services on systems where it is not required to reduce the attack surface. 4. Implement multi-factor authentication (MFA) for Remote Desktop access to add an additional layer of security beyond the vulnerable authentication mechanism. 5. Monitor Remote Desktop configuration changes and access logs for unusual or unauthorized activity to detect potential exploitation attempts early. 6. Educate users about the risks of phishing and social engineering attacks that could trigger the required user interaction for exploitation. 7. Apply network-level authentication (NLA) for Remote Desktop sessions to enforce authentication before establishing a session. 8. Use endpoint protection solutions that can detect and block suspicious activities related to Remote Desktop services. 9. Stay informed about official patches or advisories from Microsoft and apply them promptly once available.