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). This vulnerability arises due to improper handling of data within the exFAT file system driver, leading to a heap buffer overflow condition. An attacker with local access can exploit this flaw by crafting a malicious exFAT file or device that triggers the overflow when processed by the vulnerable system. Successful exploitation allows the attacker to execute arbitrary code with elevated privileges, potentially leading to full system compromise. The vulnerability requires local access and some user interaction (such as mounting or accessing a malicious exFAT volume), but no prior authentication is necessary. The CVSS v3.1 base score of 7.8 reflects a high severity, with high impact on confidentiality, integrity, and availability, and relatively low attack complexity. No known exploits are currently reported in the wild, but the vulnerability's nature and impact make it a significant risk if weaponized. The lack of available patches at the time of reporting increases the urgency for mitigation and monitoring.

For European organizations, this vulnerability poses a substantial risk, especially in environments where Windows 10 Version 1809 is still in use. The exFAT file system is commonly used for removable storage devices such as USB drives and external hard disks, which are frequently exchanged in corporate and industrial settings. An attacker could leverage this vulnerability to gain elevated privileges on targeted machines by tricking users into connecting malicious storage devices or opening crafted files. This could lead to unauthorized data access, disruption of critical services, or deployment of malware and ransomware. The impact is particularly critical for sectors with high reliance on Windows 10 legacy systems, including manufacturing, healthcare, and government agencies. Additionally, the vulnerability could facilitate lateral movement within networks if exploited on endpoint devices, amplifying the potential damage. The requirement for local access and user interaction somewhat limits remote exploitation but does not eliminate the risk posed by insider threats or social engineering attacks.

Given the absence of an official patch at the time of disclosure, European organizations should implement targeted mitigations beyond generic advice. First, restrict or disable the use of exFAT-formatted removable media on critical systems through Group Policy or endpoint management tools to reduce exposure. Employ strict device control policies to limit USB and external storage device usage, allowing only trusted devices. Enhance user awareness training to recognize and avoid connecting unknown or suspicious storage devices. Monitor system logs and endpoint detection and response (EDR) tools for unusual activity related to file system operations or privilege escalations. Where possible, upgrade affected systems to a later Windows 10 version or Windows 11 that does not contain this vulnerability. Implement application whitelisting and privilege restrictions to limit the impact of potential code execution. Finally, maintain a robust backup strategy to ensure recovery in case of compromise.