CVE-2025-29970 is a high-severity use-after-free vulnerability (CWE-416) found in the Microsoft Brokering File System component of Windows Server 2025, specifically affecting the Server Core installation variant (version 10.0.26100.0). A use-after-free vulnerability occurs when a program continues to use a pointer after the memory it points to has been freed, potentially leading to memory corruption, arbitrary code execution, or privilege escalation. In this case, the vulnerability allows an authorized local attacker—meaning someone with valid access to the system but with limited privileges—to elevate their privileges on the affected system. The CVSS v3.1 base score is 7.8, indicating a high severity, with the vector string CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C. This means the attack requires local access with low complexity and low privileges, no user interaction, and impacts confidentiality, integrity, and availability to a high degree. The scope is unchanged, so the vulnerability affects the same security authority. No known exploits are currently reported in the wild, and no patches have been linked yet. The vulnerability was reserved in March 2025 and published in May 2025. The Server Core installation is a minimalistic Windows Server installation option, often used in datacenters and enterprise environments for improved security and reduced attack surface. The Brokering File System component is responsible for managing file system operations and inter-process communications, so exploitation could allow attackers to execute arbitrary code or commands with elevated privileges, potentially compromising the entire server environment.

For European organizations, this vulnerability poses a significant risk, especially for enterprises and service providers relying on Windows Server 2025 Server Core installations for critical infrastructure, cloud services, and internal applications. Successful exploitation could allow attackers with limited local access—such as low-privileged insiders, compromised user accounts, or attackers leveraging other footholds—to escalate privileges to SYSTEM or equivalent, gaining full control over the server. This could lead to data breaches, disruption of services, deployment of ransomware, or lateral movement within networks. Given the high confidentiality, integrity, and availability impacts, organizations could face severe operational disruptions and regulatory consequences under GDPR if sensitive personal data is exposed or manipulated. The lack of known public exploits provides a window for proactive mitigation, but the presence of a local privilege escalation vulnerability in a core server OS component necessitates urgent attention to prevent potential targeted attacks.

Organizations should prioritize deploying official patches from Microsoft as soon as they become available. Until patches are released, practical mitigations include: 1) Restricting local access to Windows Server 2025 Server Core systems by enforcing strict access controls and monitoring local logins; 2) Implementing robust endpoint detection and response (EDR) solutions to detect anomalous privilege escalation attempts; 3) Applying the principle of least privilege rigorously to limit the number of users with local access and administrative rights; 4) Utilizing Windows Defender Application Control (WDAC) or similar whitelisting technologies to prevent unauthorized code execution; 5) Monitoring system logs and security events for suspicious activity related to the Brokering File System or unexpected process behaviors; 6) Employing network segmentation to isolate critical servers and limit lateral movement in case of compromise; 7) Conducting regular security audits and vulnerability assessments focused on Windows Server environments; 8) Preparing incident response plans specifically addressing privilege escalation scenarios. These measures help reduce the attack surface and improve detection capabilities until a patch is applied.