CVE-2025-55701 is a vulnerability identified in Microsoft Windows 11 Version 25H2 (build 10.0.26200.0), categorized under CWE-1287, which relates to improper validation of the specified type of input. This flaw allows an authorized local attacker—meaning someone with existing access to the system but with limited privileges—to escalate their privileges to a higher level, potentially SYSTEM or administrator. The root cause is insufficient validation of input types, which could be exploited by crafting specific inputs that bypass security checks, leading to unauthorized code execution or modification of system settings. The vulnerability does not require user interaction, making it more dangerous once local access is obtained. The CVSS v3.1 base score is 7.8, indicating high severity, with metrics AV:L (local attack vector), AC:L (low attack complexity), PR:L (low privileges required), UI:N (no user interaction), and full impact on confidentiality, integrity, and availability. Although no known exploits are currently reported in the wild, the vulnerability’s characteristics suggest it could be leveraged in targeted attacks or combined with other vulnerabilities for broader compromise. The vulnerability was reserved in August 2025 and published in October 2025, but no official patches have been linked yet, emphasizing the need for vigilance. This vulnerability is particularly critical for environments where Windows 11 25H2 is deployed, as attackers with local access could gain full control over affected systems.

For European organizations, this vulnerability poses a significant risk, especially in sectors relying heavily on Windows 11 25H2, such as finance, healthcare, government, and critical infrastructure. Successful exploitation can lead to unauthorized access to sensitive data, disruption of services, and potential lateral movement within networks. The elevation of privileges could allow attackers to disable security controls, install persistent malware, or exfiltrate confidential information, severely impacting confidentiality, integrity, and availability. Organizations with remote or shared access environments are particularly vulnerable if attackers can gain initial footholds. The lack of user interaction requirement increases the risk of automated or stealthy exploitation once local access is achieved. This could undermine trust in IT systems and lead to regulatory non-compliance, especially under GDPR and other European data protection laws.

Immediate mitigation steps include restricting local access to trusted users only and enforcing strict access controls on endpoints running Windows 11 25H2. Employ application whitelisting and endpoint detection and response (EDR) solutions to monitor for suspicious privilege escalation attempts. Regularly audit user permissions and remove unnecessary local privileges to reduce the attack surface. Network segmentation can limit lateral movement if an attacker gains local access. Organizations should monitor Microsoft security advisories closely and apply patches promptly once available. Until patches are released, consider deploying temporary workarounds such as disabling vulnerable components if identified or using group policies to limit the execution of untrusted code. Additionally, implement robust logging and alerting to detect anomalous activities indicative of exploitation attempts. Employee training on the risks of local access compromise can also reduce insider threats.