CVE-2024-38135 is a high-severity elevation of privilege vulnerability affecting Microsoft Windows 11 Version 24H2, specifically version 10.0.26100.0. The vulnerability arises from a buffer over-read condition (classified under CWE-126) within the Windows Resilient File System (ReFS) implementation. Buffer over-read occurs when a program reads more data than the buffer it allocated, potentially leading to information disclosure or memory corruption. In this case, the flaw allows an attacker with limited privileges (local privileges) to exploit the vulnerability without requiring user interaction. The attacker can leverage this flaw to escalate their privileges on the affected system, gaining higher-level access than originally permitted. The CVSS v3.1 base score is 7.8, indicating a high severity level, with the vector string CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C. This means the attack requires local access with low attack complexity and low privileges, no user interaction, and impacts confidentiality, integrity, and availability to a high degree. The vulnerability does not currently have known exploits in the wild, but the presence of a publicly assigned CVE and a high CVSS score suggests that it is a significant risk if left unpatched. No official patch links are provided yet, indicating that mitigation may currently rely on workarounds or awaiting vendor updates. The vulnerability affects the ReFS file system, which is used primarily in enterprise and server environments for its resilience and data integrity features, but it is also supported on Windows 11 client systems, especially in professional and enterprise editions.

For European organizations, this vulnerability poses a substantial risk, particularly for enterprises and government agencies using Windows 11 Version 24H2 with ReFS volumes. Successful exploitation could allow attackers with limited local access—such as through compromised user accounts or insider threats—to escalate privileges to SYSTEM or administrative levels. This could lead to full system compromise, unauthorized access to sensitive data, disruption of critical services, and potential lateral movement within networks. The high impact on confidentiality, integrity, and availability means that sensitive personal data protected under GDPR could be exposed or altered, leading to regulatory and reputational consequences. Additionally, organizations relying on ReFS for data integrity and resilience in storage systems may face increased risk of data corruption or loss if attackers exploit this flaw to manipulate file system structures. Although no known exploits are currently in the wild, the vulnerability's characteristics make it a likely target for attackers once exploit code becomes available, especially in environments where patching is delayed or incomplete.

To mitigate this vulnerability, European organizations should prioritize the following actions: 1) Monitor Microsoft security advisories closely for the release of official patches addressing CVE-2024-38135 and apply them promptly once available. 2) Restrict local access to systems running Windows 11 Version 24H2 with ReFS volumes by enforcing strict access controls, limiting administrative privileges, and employing the principle of least privilege. 3) Implement robust endpoint detection and response (EDR) solutions capable of detecting unusual privilege escalation attempts or anomalous file system activity related to ReFS. 4) Conduct regular audits of user accounts and permissions to identify and remove unnecessary local accounts or privileges that could be leveraged by attackers. 5) Consider temporarily disabling or avoiding the use of ReFS volumes on client systems where feasible until patches are applied, especially in high-risk environments. 6) Enhance network segmentation to limit the impact of potential compromises and prevent lateral movement. 7) Educate IT staff and users about the risks of local privilege escalation vulnerabilities and the importance of maintaining updated systems. These measures, combined with timely patching, will reduce the attack surface and limit the potential for exploitation.