CVE-2025-55339 is an out-of-bounds read vulnerability classified under CWE-125 affecting the Network Driver Interface Specification (NDIS) component in Microsoft Windows 11 Version 25H2 (build 10.0.26200.0). The flaw arises when the NDIS driver improperly handles memory boundaries, allowing an authorized local attacker to read memory beyond allocated buffers. This can lead to privilege escalation by exposing sensitive kernel memory or corrupting internal data structures, potentially enabling the attacker to execute arbitrary code with elevated privileges or cause system crashes. The vulnerability requires local access and does not need user interaction, making it a significant risk in environments where multiple users or processes share access. The CVSS v3.1 score of 7.8 reflects high impact on confidentiality, integrity, and availability, with low attack complexity and limited privileges required. Although no public exploits are known yet, the vulnerability's nature suggests it could be leveraged in targeted attacks or lateral movement scenarios. The absence of an official patch at the time of publication necessitates proactive mitigation and monitoring. This vulnerability is particularly critical for enterprise environments relying on Windows 11 25H2, as it undermines the security boundary between user and kernel modes.

For European organizations, the impact of CVE-2025-55339 is substantial. Successful exploitation can lead to local privilege escalation, allowing attackers to gain administrative control over affected systems. This compromises confidentiality by exposing sensitive data in memory, integrity by enabling unauthorized code execution or system modifications, and availability by potentially causing system crashes or instability. Organizations with multi-user environments, such as shared workstations or terminal servers, face increased risk due to the local access requirement. Critical infrastructure, government agencies, financial institutions, and enterprises with sensitive intellectual property are particularly vulnerable. The vulnerability could facilitate lateral movement within networks, increasing the scope of compromise. Given the widespread deployment of Windows 11 in European enterprises and public sector entities, the threat could have broad operational and reputational consequences if exploited.

Immediate mitigation steps include restricting local access to trusted users only, enforcing strict access controls on workstations and servers running Windows 11 Version 25H2, and monitoring for unusual local privilege escalation attempts. Organizations should implement application whitelisting and endpoint detection and response (EDR) solutions to detect anomalous behavior indicative of exploitation attempts. Until an official patch is released, consider isolating critical systems or limiting user privileges to reduce attack surface. Regularly audit and harden local user accounts and group memberships. Once Microsoft releases a security update addressing this vulnerability, prioritize its deployment across all affected systems. Additionally, conduct thorough post-patch testing to ensure stability and verify that the vulnerability is remediated. Security teams should also review internal incident response plans to quickly address any signs of exploitation.