CVE-2025-47991 is a use-after-free vulnerability classified under CWE-416 found in the Microsoft Input Method Editor (IME) component of Windows 10 Version 1607 (build 14393.0). This vulnerability arises when the IME improperly manages memory, freeing an object while it is still in use, which can lead to arbitrary code execution or corruption of memory. An attacker with authorized local access and low privileges can exploit this flaw to elevate their privileges to SYSTEM level, thereby gaining full control over the affected system. The vulnerability does not require user interaction but does require local access, making remote exploitation infeasible without prior access. The CVSS v3.1 base score is 7.8, reflecting high severity due to the potential impact on confidentiality, integrity, and availability, combined with the complexity of the attack and the requirement for local privileges. No public exploits or active exploitation in the wild have been reported to date. The vulnerability is particularly concerning for environments that still operate Windows 10 Version 1607, which is an older, out-of-support version, increasing the risk due to lack of official patches. The flaw can be leveraged by attackers to bypass security boundaries, execute arbitrary code with elevated privileges, and potentially deploy malware or ransomware. The vulnerability's presence in the IME component, which handles input methods, means it could be triggered during normal user input operations, increasing the attack surface. Microsoft has not yet released patches, so mitigation currently relies on limiting local access and upgrading to supported Windows versions.

For European organizations, the impact of CVE-2025-47991 is significant, especially for those still running legacy Windows 10 Version 1607 systems. Successful exploitation allows attackers to escalate privileges locally, potentially leading to full system compromise. This can result in unauthorized access to sensitive data, disruption of critical services, and deployment of persistent malware or ransomware. Sectors such as government, finance, healthcare, and critical infrastructure are particularly at risk due to the sensitive nature of their data and operations. The vulnerability undermines confidentiality, integrity, and availability, threatening compliance with data protection regulations like GDPR. Since the attack requires local access, insider threats or attackers who have gained initial footholds via other means could leverage this vulnerability to deepen their control. The lack of patches increases the window of exposure, making timely mitigation critical. Organizations relying on legacy systems may face operational challenges in upgrading but must prioritize remediation to avoid exploitation.

1. Upgrade affected systems from Windows 10 Version 1607 to a supported and fully patched Windows version (e.g., Windows 10 21H2 or later). 2. Until patches are available, enforce strict local access controls, including limiting administrative privileges and using least privilege principles. 3. Implement application whitelisting and endpoint detection and response (EDR) solutions to detect and block suspicious local privilege escalation attempts. 4. Monitor system logs and security events for unusual IME activity or unexpected process behavior indicative of exploitation attempts. 5. Disable or restrict use of IME components if feasible in the organizational context to reduce attack surface. 6. Conduct user awareness training to reduce insider threat risks and encourage reporting of suspicious activity. 7. Maintain up-to-date backups and incident response plans to recover quickly if compromise occurs. 8. Engage with Microsoft support channels for any out-of-band patches or mitigations once released.