CVE-2025-64661 is a race condition vulnerability classified under CWE-362, affecting the Windows Shell component in Microsoft Windows 10 Version 1809 (build 10.0.17763.0). The vulnerability stems from improper synchronization when multiple threads or processes concurrently access shared resources within the Windows Shell, leading to a race condition. This flaw allows an authorized local attacker to exploit the timing window to execute code or operations with elevated privileges, bypassing normal security restrictions. The attack vector is local (AV:L), requiring the attacker to have low privileges (PR:L) but no user interaction (UI:N). The attack complexity is high (AC:H), indicating that exploitation demands precise conditions or timing. The vulnerability impacts confidentiality, integrity, and availability (C:H/I:H/A:H) and has a scope change (S:C), meaning the attacker can affect resources beyond their initial privileges. Although no known exploits are currently in the wild, the vulnerability poses a significant risk due to the potential for privilege escalation, which can lead to full system compromise. No patches have been released yet, and the vulnerability was published on December 9, 2025. The lack of patch availability necessitates immediate mitigation efforts to reduce exposure. The vulnerability is particularly relevant for environments still running Windows 10 Version 1809, which, despite being an older release, remains in use in some organizations due to legacy application dependencies or delayed upgrade cycles.

For European organizations, this vulnerability presents a significant risk, especially for entities relying on Windows 10 Version 1809 in critical infrastructure, government, finance, and healthcare sectors. Successful exploitation allows attackers with local access to escalate privileges, potentially leading to full system compromise, data breaches, unauthorized access to sensitive information, and disruption of services. The high impact on confidentiality, integrity, and availability means that attackers could install persistent malware, exfiltrate data, or disrupt operations. Given the high attack complexity and requirement for local access, the threat is more pronounced in environments where endpoint security is weak or where insider threats exist. Organizations with legacy systems or delayed patch management cycles are particularly vulnerable. Additionally, the absence of known exploits in the wild currently provides a window for proactive defense but also underscores the urgency for mitigation before exploit code becomes available.

1. Restrict local access to systems running Windows 10 Version 1809 by enforcing strict access controls and limiting user privileges to the minimum necessary. 2. Implement application whitelisting and endpoint detection and response (EDR) solutions to monitor and block suspicious local activities indicative of exploitation attempts. 3. Enforce network segmentation to isolate critical systems and reduce the risk of lateral movement following privilege escalation. 4. Conduct thorough audits of user accounts and remove or disable unnecessary local accounts to minimize potential attackers. 5. Encourage or mandate upgrades to supported Windows versions with active security updates to eliminate exposure to this vulnerability. 6. Monitor security advisories from Microsoft for the release of patches or workarounds and apply them promptly once available. 7. Educate IT staff and users about the risks of local privilege escalation and the importance of reporting unusual system behavior. 8. Use security tools capable of detecting race condition exploitation patterns, if available, to enhance detection capabilities.