CVE-2025-21180 is a heap-based buffer overflow vulnerability identified in the exFAT file system driver of Microsoft Windows 10 Version 1809 (build 10.0.17763.0). The vulnerability arises from improper handling of data structures within the exFAT driver, leading to a condition where an attacker can overflow a heap buffer. This overflow can corrupt adjacent memory, enabling arbitrary code execution in the context of the local user. The flaw does not require elevated privileges (PR:N) but does require user interaction (UI:R), such as opening or mounting a specially crafted exFAT-formatted storage device or file. The vulnerability affects confidentiality, integrity, and availability (C:H/I:H/A:H), meaning an attacker could execute malicious code, potentially gaining control over the affected system or causing system crashes. The CVSS vector indicates low attack complexity (AC:L) and local attack vector (AV:L), emphasizing that the attacker must have local access but no special privileges. No known exploits have been reported in the wild yet, but the vulnerability is publicly disclosed and rated with a high CVSS score of 7.8, indicating a significant risk. The absence of patch links suggests that a fix may be forthcoming or pending deployment. The vulnerability is tracked under CWE-122, a common weakness related to heap-based buffer overflows, which are often exploited for remote code execution or privilege escalation. Given the nature of exFAT as a widely used file system for removable media, the attack surface includes USB drives and other external storage devices formatted with exFAT.

For European organizations, this vulnerability poses a significant risk, particularly for those using Windows 10 Version 1809 in environments where removable media is common, such as manufacturing, healthcare, and government sectors. Successful exploitation could lead to arbitrary code execution, allowing attackers to install malware, steal sensitive data, disrupt operations, or move laterally within networks. The impact on confidentiality, integrity, and availability is high, potentially leading to data breaches, system downtime, and loss of trust. Organizations with legacy systems that have not been updated or isolated are especially vulnerable. Additionally, sectors with strict regulatory requirements for data protection (e.g., GDPR) may face compliance risks if this vulnerability is exploited. The local attack vector and requirement for user interaction limit remote exploitation but do not eliminate risk, as insider threats or social engineering could facilitate attacks. The lack of known exploits in the wild provides a window for proactive mitigation before active exploitation occurs.

1. Prioritize patching: Monitor Microsoft security advisories closely and apply patches for Windows 10 Version 1809 exFAT driver as soon as they become available. 2. Restrict local access: Limit physical and logical access to systems running the vulnerable OS version, especially restricting the use of removable media. 3. Disable or restrict exFAT support: Where feasible, disable exFAT file system support or restrict mounting of exFAT-formatted devices via group policies or endpoint protection tools. 4. Implement application whitelisting and endpoint detection: Use advanced endpoint protection solutions to detect anomalous behavior related to file system operations and code execution attempts. 5. User awareness training: Educate users about the risks of connecting untrusted removable media and the importance of avoiding suspicious files or devices. 6. Network segmentation: Isolate critical systems running legacy Windows 10 versions to contain potential compromises. 7. Monitor logs and alerts: Enable detailed logging of file system events and monitor for unusual activity that could indicate exploitation attempts. 8. Plan for OS upgrades: Develop a roadmap to migrate from Windows 10 Version 1809 to supported, updated versions to reduce exposure to legacy vulnerabilities.