CVE-2025-55699 is a vulnerability classified under CWE-200 (Exposure of Sensitive Information to an Unauthorized Actor) affecting Microsoft Windows 11 Version 25H2 (build 10.0.26200.0). The vulnerability resides in the Windows kernel and allows an attacker who already has local authorized access (i.e., a user with some level of privileges on the system) to disclose sensitive information that should be protected. The flaw does not require user interaction and does not impact the integrity or availability of the system, focusing solely on confidentiality breaches. The CVSS v3.1 score is 5.5 (medium severity), with attack vector local (AV:L), low attack complexity (AC:L), privileges required low (PR:L), no user interaction (UI:N), and scope unchanged (S:U). The vulnerability was reserved in August 2025 and published in October 2025, with no known exploits in the wild and no patches released at the time of this report. The exposure of sensitive kernel information could allow attackers to gain insights that facilitate further attacks or data exfiltration. Since the attacker must have local access and some privileges, the threat is primarily relevant in multi-user environments, shared systems, or where insider threats exist. The absence of patches necessitates heightened vigilance and interim mitigations.

For European organizations, the primary impact of CVE-2025-55699 is the potential unauthorized disclosure of sensitive information from Windows 11 25H2 systems. This can lead to confidentiality breaches affecting intellectual property, personal data, or security-related information stored or processed on affected endpoints. Organizations with shared workstations, virtual desktop infrastructure, or environments where multiple users have local access are at increased risk. Although the vulnerability does not directly compromise system integrity or availability, the leaked information could be leveraged to mount more severe attacks, including privilege escalation or lateral movement. Critical sectors such as finance, government, healthcare, and energy in Europe could face heightened risks if attackers exploit this vulnerability to gather sensitive kernel data. The lack of known exploits currently reduces immediate risk, but the medium severity rating and kernel-level exposure warrant proactive measures. The impact is mitigated somewhat by the requirement for local access and privileges, limiting remote exploitation possibilities.

1. Enforce strict local access controls and limit user privileges to the minimum necessary to reduce the pool of potential attackers with local access. 2. Monitor and audit local user activities for unusual behavior that could indicate attempts to exploit this vulnerability. 3. Implement endpoint detection and response (EDR) solutions capable of detecting suspicious kernel-level information access patterns. 4. Isolate sensitive systems and restrict physical and remote access to trusted personnel only. 5. Apply the official Microsoft security updates and patches as soon as they become available for Windows 11 Version 25H2. 6. Use application whitelisting and privilege management tools to prevent unauthorized code execution or privilege escalation attempts. 7. Educate users about the risks of local privilege misuse and insider threats. 8. Consider deploying additional kernel integrity monitoring tools to detect anomalous kernel memory access. 9. For virtualized environments, ensure hypervisor and guest OS security best practices are followed to prevent cross-VM attacks. 10. Regularly review and update security policies to incorporate emerging threat intelligence related to Windows kernel vulnerabilities.