CVE-2025-55233 is an out-of-bounds read vulnerability classified under CWE-125 affecting the Windows Projected File System (ProjFS) in Microsoft Windows 11 Version 25H2 (build 10.0.26200.0). ProjFS is a component that enables virtualization of file system data, allowing applications to project hierarchical data as files and folders. The vulnerability arises when the component improperly handles memory boundaries during file system operations, allowing an attacker with authorized local access and limited privileges to read memory beyond allocated buffers. This can lead to disclosure of sensitive information and potentially enable privilege escalation by corrupting or leaking critical data structures. The CVSS v3.1 base score is 7.8, indicating high severity, with attack vector local (AV:L), low attack complexity (AC:L), privileges required (PR:L), no user interaction (UI:N), and impact on confidentiality, integrity, and availability all rated high (C:H/I:H/A:H). The vulnerability scope is unchanged (S:U), meaning the impact is confined to the vulnerable component on the local system. Although no exploits are known in the wild yet, the vulnerability's characteristics make it a significant risk for local attackers aiming to elevate privileges. No official patches or mitigation links have been published as of now, but Microsoft is expected to release updates. The vulnerability was reserved in August 2025 and published in December 2025.

For European organizations, the impact of CVE-2025-55233 can be substantial. Since Windows 11 is widely deployed across enterprises and government agencies, especially in sectors like finance, healthcare, and critical infrastructure, this vulnerability could allow attackers with limited local access to escalate privileges and gain control over affected systems. This could lead to unauthorized access to sensitive data, disruption of services, and potential lateral movement within networks. Organizations relying on Windows 11 25H2 for endpoint devices, servers, or specialized applications that use ProjFS are particularly at risk. The confidentiality, integrity, and availability of systems could be compromised, resulting in data breaches, operational downtime, and reputational damage. The lack of known exploits currently provides a window for proactive defense, but the high severity score underscores the urgency of mitigation.

To mitigate CVE-2025-55233 effectively, European organizations should: 1) Restrict local access to systems running Windows 11 Version 25H2, enforcing strict access controls and least privilege principles to minimize the number of users who can execute code locally. 2) Monitor system logs and behavior for unusual file system activity or privilege escalation attempts, focusing on ProjFS-related operations. 3) Implement application whitelisting and endpoint detection and response (EDR) solutions to detect and block suspicious processes. 4) Prepare for rapid deployment of official patches from Microsoft once released; establish a patch management process prioritizing this vulnerability. 5) Conduct internal audits to identify systems running the affected build and isolate or harden them until patches are applied. 6) Educate IT staff about the vulnerability specifics to recognize potential exploitation signs. 7) Consider network segmentation to limit the impact of a compromised endpoint. These targeted actions go beyond generic advice by focusing on the local access requirement and the specific component involved.