CVE-2025-49678 is a high-severity vulnerability identified in Microsoft Windows 10 Version 1809 (build 10.0.17763.0) involving a null pointer dereference within the Windows NTFS file system driver. This vulnerability arises when the system attempts to dereference a null pointer, leading to undefined behavior that can be exploited by an authorized local attacker to elevate their privileges. Specifically, the flaw allows an attacker with limited privileges (low privileges) to execute code or perform actions with higher privileges, potentially SYSTEM-level, by triggering the null pointer dereference condition. The vulnerability is classified under CWE-476 (NULL Pointer Dereference) and is related to improper handling of memory references, which can cause system instability or crashes. The CVSS v3.1 base score is 7.0, indicating a high severity level, with the vector string showing that the attack requires local access (AV:L), high attack complexity (AC:H), low privileges (PR:L), no user interaction (UI:N), and impacts confidentiality, integrity, and availability at a high level (C:H/I:H/A:H). The scope remains unchanged (S:U), meaning the vulnerability affects the same security scope. No known exploits are currently reported in the wild, and no patches or mitigation links are provided yet. The vulnerability's exploitation could allow attackers to bypass security controls and gain unauthorized access to sensitive system resources or data, potentially leading to system compromise or denial of service.

For European organizations, this vulnerability poses a significant risk, especially for those still operating legacy systems or environments running Windows 10 Version 1809. The ability for a local attacker to escalate privileges can lead to lateral movement within corporate networks, unauthorized access to sensitive data, and disruption of critical services. Given the high impact on confidentiality, integrity, and availability, exploitation could result in data breaches, loss of data integrity, and operational downtime. Organizations in sectors such as finance, healthcare, government, and critical infrastructure are particularly at risk due to the sensitive nature of their data and the regulatory requirements for data protection under GDPR and other European regulations. Additionally, the lack of a patch at the time of publication means organizations must rely on compensating controls to mitigate risk. The high attack complexity and requirement for local access somewhat limit remote exploitation, but insider threats or compromised endpoints could still leverage this vulnerability effectively.

Since no official patch is currently available, European organizations should implement the following specific mitigation strategies: 1) Restrict local access strictly by enforcing the principle of least privilege and limiting administrative rights to essential personnel only. 2) Employ application whitelisting and endpoint protection solutions capable of detecting abnormal behavior indicative of privilege escalation attempts. 3) Monitor system logs and audit events related to NTFS and privilege escalation activities to detect early signs of exploitation. 4) Isolate legacy systems running Windows 10 Version 1809 from critical network segments and sensitive data repositories to reduce the attack surface. 5) Implement strict user session controls and endpoint hardening to prevent unauthorized local access. 6) Prepare for rapid deployment of patches once released by Microsoft by maintaining an up-to-date asset inventory and patch management process. 7) Conduct user awareness training focusing on insider threat risks and the importance of reporting suspicious system behavior. These targeted actions go beyond generic advice by focusing on controlling local access vectors and monitoring NTFS-related activities.