CVE-2025-47991 is a high-severity use-after-free vulnerability (CWE-416) found in the Microsoft Input Method Editor (IME) component of Windows 10 Version 1809 (build 10.0.17763.0). The vulnerability allows an authorized local attacker with limited privileges to execute a use-after-free condition, which can lead to memory corruption. Exploiting this flaw enables the attacker to elevate their privileges on the affected system, potentially gaining SYSTEM-level access. The vulnerability does not require user interaction but does require local access with some privileges. The CVSS v3.1 base score is 7.8, reflecting high impact on confidentiality, integrity, and availability, with an attack vector limited to local access and a high attack complexity. The scope is changed, indicating that the vulnerability affects resources beyond the initially vulnerable component. No known exploits are currently reported in the wild, and no patches have been linked yet. The vulnerability was reserved in May 2025 and published in July 2025, indicating recent discovery. The IME component is critical for text input and language support, and exploitation could allow attackers to bypass security controls and execute arbitrary code with elevated privileges, compromising system integrity and confidentiality.

For European organizations, this vulnerability poses a significant risk, especially for enterprises and government agencies still running Windows 10 Version 1809, which is an older but still in-use OS version in some sectors. Successful exploitation could allow attackers to escalate privileges from a limited user account to SYSTEM, enabling full control over affected machines. This could lead to data breaches, unauthorized access to sensitive information, disruption of services, and potential lateral movement within networks. Organizations relying on legacy systems or with delayed patch management processes are particularly vulnerable. The lack of known exploits in the wild currently reduces immediate risk, but the high severity and potential impact necessitate proactive mitigation. The vulnerability could also be leveraged in targeted attacks against high-value assets such as critical infrastructure, financial institutions, and government networks within Europe.

1. Immediate mitigation should focus on upgrading affected systems to a supported and patched version of Windows 10 or later, as Windows 10 Version 1809 is outdated and may no longer receive security updates. 2. If upgrading is not immediately feasible, organizations should implement strict access controls to limit local user privileges and restrict who can log on locally to critical systems. 3. Employ application whitelisting and endpoint detection and response (EDR) solutions to monitor for suspicious activity indicative of exploitation attempts. 4. Disable or restrict the use of the Microsoft Input Method Editor (IME) component where possible, especially on systems that do not require complex input methods. 5. Monitor security advisories from Microsoft for the release of official patches and apply them promptly once available. 6. Conduct regular audits of local user accounts and privilege assignments to minimize the attack surface. 7. Educate IT staff and users about the risks of local privilege escalation vulnerabilities and the importance of timely updates.