CVE-2025-26679 is a high-severity use-after-free vulnerability (CWE-416) identified in the Microsoft Windows 10 Version 1809 operating system, specifically affecting build 10.0.17763.0. The vulnerability resides in the RPC Endpoint Mapper Service, a critical component responsible for mapping RPC requests to the appropriate service endpoints. The flaw allows an authorized local attacker to exploit a use-after-free condition, which occurs when the system attempts to access memory after it has been freed. This can lead to memory corruption, enabling the attacker to execute arbitrary code with elevated privileges. The vulnerability requires local access and some level of privileges (PR:L), but does not require user interaction (UI:N). The CVSS v3.1 base score is 7.8, reflecting high impact on confidentiality, integrity, and availability (all rated high), with low attack complexity and no user interaction needed. Although no known exploits are currently reported in the wild, the vulnerability's nature and impact make it a significant risk, especially in environments where Windows 10 Version 1809 is still in use. The lack of an official patch link suggests that remediation may not yet be available, emphasizing the need for immediate mitigation efforts. This vulnerability could be leveraged by attackers to escalate privileges locally, potentially leading to full system compromise or lateral movement within a network.

For European organizations, the impact of CVE-2025-26679 can be substantial, particularly in sectors relying on legacy Windows 10 Version 1809 systems. Successful exploitation could allow attackers to elevate privileges from a low-privileged user account to SYSTEM-level access, compromising sensitive data confidentiality, system integrity, and availability. This is especially critical for organizations handling personal data under GDPR, as breaches could lead to regulatory penalties and reputational damage. The vulnerability could facilitate insider threats or be used in multi-stage attacks where initial access is limited. Given the RPC Endpoint Mapper Service's role in network communications, exploitation might also enable attackers to disrupt services or propagate malware laterally. European enterprises with legacy infrastructure, including government agencies, healthcare providers, and financial institutions, face increased risk due to the potential for privilege escalation and subsequent control over critical systems.

Given the absence of an official patch, European organizations should implement immediate compensating controls. These include restricting local user permissions to the minimum necessary, employing application whitelisting to prevent execution of unauthorized code, and enabling enhanced auditing and monitoring of RPC service activities to detect anomalous behavior. Network segmentation should be enforced to limit access to vulnerable systems, and legacy Windows 10 Version 1809 machines should be prioritized for upgrade to supported Windows versions with security updates. Additionally, organizations should deploy endpoint detection and response (EDR) solutions capable of identifying exploitation attempts related to use-after-free conditions. Administrators should also review and harden RPC service configurations and consider disabling unnecessary RPC services where feasible. Finally, maintaining robust incident response plans tailored to privilege escalation scenarios will help mitigate potential damage.