CVE-2025-55694 is a vulnerability classified under CWE-284 (Improper Access Control) found in the Windows Error Reporting (WER) component of Microsoft Windows 11 Version 25H2 (build 10.0.26200.0). The flaw arises because WER does not adequately enforce access control policies, allowing an attacker who already has some level of local access (i.e., an authorized but non-privileged user) to escalate their privileges to a higher level, potentially SYSTEM or administrator privileges. This escalation occurs without requiring user interaction, which increases the risk of automated or stealthy exploitation. The vulnerability affects the confidentiality, integrity, and availability of the system since an attacker could gain full control, access sensitive data, modify system configurations, or disrupt services. The CVSS v3.1 base score of 7.8 indicates a high severity, with attack vector local (AV:L), low attack complexity (AC:L), privileges required (PR:L), no user interaction (UI:N), and impacts to confidentiality, integrity, and availability all rated high (C:H/I:H/A:H). No public exploits have been reported yet, but the vulnerability was reserved in August 2025 and published in October 2025, suggesting recent discovery and disclosure. The lack of available patches at the time of reporting means organizations must rely on interim mitigations until official updates are released by Microsoft. This vulnerability highlights the criticality of access control in system components that handle error reporting, as improper controls can be leveraged for privilege escalation.

For European organizations, this vulnerability poses a significant risk due to the widespread adoption of Windows 11 in enterprise environments. Successful exploitation can lead to full system compromise, enabling attackers to access sensitive corporate data, disrupt business operations, or move laterally within networks. Critical sectors such as finance, healthcare, government, and energy, which rely heavily on Windows endpoints, could face severe operational and reputational damage. The local attack vector means that insider threats or attackers who have gained initial footholds through other means (e.g., phishing, credential theft) can leverage this vulnerability to escalate privileges and deepen their access. The absence of user interaction requirement facilitates automated exploitation in compromised environments. Given the high impact on confidentiality, integrity, and availability, organizations may experience data breaches, ransomware deployment, or sabotage of critical infrastructure. The threat is amplified in environments with weak local user privilege management or insufficient monitoring of privilege escalation attempts.

Until Microsoft releases an official patch, European organizations should implement several targeted mitigations: 1) Enforce the principle of least privilege by restricting local user permissions and removing unnecessary administrative rights. 2) Harden Windows Error Reporting settings via Group Policy or registry to limit its capabilities or disable it temporarily if feasible without impacting critical diagnostics. 3) Deploy endpoint detection and response (EDR) solutions configured to detect anomalous privilege escalation behaviors and monitor WER-related processes. 4) Conduct regular audits of local accounts and privilege assignments to identify and remediate excessive permissions. 5) Implement application whitelisting to prevent unauthorized code execution that could exploit this vulnerability. 6) Educate IT staff and users about the risk of local privilege escalation and the importance of reporting suspicious activity. 7) Prepare for rapid deployment of Microsoft patches once available by testing updates in controlled environments. 8) Use network segmentation to limit lateral movement opportunities if an attacker gains local access. These measures go beyond generic advice by focusing on controlling local user privileges and monitoring the specific component involved.