CVE-2025-49659 is a high-severity vulnerability identified in Microsoft Windows 10 Version 1809 (build 10.0.17763.0). The flaw is a buffer over-read issue located in the Windows TDX.sys component. TDX.sys is related to Trusted Domain Extensions, a kernel-mode driver that handles virtualization and security features. The vulnerability is classified under CWE-126, which involves improper buffer handling that allows reading beyond the intended memory bounds. An authorized attacker with local access and limited privileges can exploit this vulnerability to perform a privilege escalation attack, gaining higher system privileges without requiring user interaction. The CVSS v3.1 score of 7.8 reflects a high severity due to the combination of local attack vector, low attack complexity, required privileges, and the significant impact on confidentiality, integrity, and availability. Although no known exploits are currently reported in the wild, the vulnerability’s nature and impact make it a critical concern for affected systems. The absence of available patches at the time of publication increases the urgency for mitigation and monitoring. This vulnerability specifically affects Windows 10 Version 1809, an older but still in-use version of Windows 10, which may be present in legacy systems or environments where updates are delayed or restricted.

For European organizations, the impact of CVE-2025-49659 can be substantial, especially in sectors relying on Windows 10 Version 1809 for legacy applications or specialized hardware compatibility. Successful exploitation allows attackers to escalate privileges locally, potentially leading to full system compromise, unauthorized access to sensitive data, disruption of critical services, and lateral movement within networks. This can affect confidentiality by exposing sensitive information, integrity by allowing unauthorized changes to system configurations or data, and availability by enabling denial-of-service conditions through system instability or crashes. Organizations in regulated industries such as finance, healthcare, and critical infrastructure may face compliance violations and reputational damage if exploited. The local attack vector means that attackers must have some level of access already, which could be achieved via phishing, insider threats, or other initial access methods. The lack of user interaction requirement increases the risk of automated or stealthy exploitation once local access is obtained. Given the high severity and broad impact on core system security, European organizations must prioritize addressing this vulnerability to maintain operational security and trust.

1. Immediate mitigation should focus on restricting local access to systems running Windows 10 Version 1809, limiting user privileges to the minimum necessary, and monitoring for suspicious local activity indicative of privilege escalation attempts. 2. Implement strict access controls and network segmentation to reduce the risk of attackers gaining local access to vulnerable machines. 3. Deploy endpoint detection and response (EDR) solutions capable of identifying anomalous behavior related to privilege escalation and kernel driver exploitation. 4. Since no patches are currently available, consider upgrading affected systems to a supported and fully patched Windows version where this vulnerability is resolved. 5. Apply application whitelisting and kernel-mode driver signing enforcement to prevent unauthorized or malicious driver loading. 6. Conduct regular security audits and vulnerability assessments focusing on legacy systems to identify and remediate similar risks. 7. Educate users and administrators about the risks of local privilege escalation and enforce strong authentication and session management policies to limit attacker footholds. 8. Monitor official Microsoft channels for patch releases and apply updates promptly once available.