CVE-2025-49679 is a numeric truncation error vulnerability identified in the Windows Shell component of Microsoft Windows 10 Version 1809 (build 10.0.17763.0). This vulnerability arises from improper handling of numeric data, specifically a truncation error, which can lead to incorrect processing of values within the Windows Shell. An authorized attacker with local access can exploit this flaw to elevate their privileges on the affected system. The vulnerability is classified under CWE-197, which concerns numeric truncation errors that occur when a numeric value is converted to a type that is too small to hold it, potentially causing data corruption or unexpected behavior. The CVSS v3.1 base score is 7.8, indicating a high severity level. The vector string (AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H) shows that the attack requires local access with low complexity, low privileges, and no user interaction, but can result in high impact on confidentiality, integrity, and availability. The scope remains unchanged, meaning the vulnerability affects only the vulnerable component. No known exploits are currently in the wild, and no patches have been linked yet. Given the affected product is Windows 10 Version 1809, which is an older version of Windows 10, systems still running this version are at risk if unpatched. The vulnerability allows an attacker to escalate privileges locally, potentially enabling them to execute code with higher privileges, access sensitive data, or disrupt system operations.

For European organizations, this vulnerability poses a significant risk especially in environments where Windows 10 Version 1809 is still in use, such as legacy systems or specialized industrial setups. Successful exploitation could allow attackers to gain elevated privileges, bypassing security controls and potentially leading to unauthorized access to sensitive information, disruption of critical services, or deployment of further malware. This is particularly concerning for sectors with stringent data protection requirements like finance, healthcare, and government institutions across Europe. The high impact on confidentiality, integrity, and availability means that exploitation could result in data breaches, system downtime, and loss of trust. Additionally, since the attack requires only local access, insider threats or attackers who have gained initial footholds through other means could leverage this vulnerability to escalate privileges and move laterally within networks. The lack of user interaction needed further increases the risk of automated or stealthy exploitation once local access is obtained.

European organizations should prioritize identifying and inventorying systems running Windows 10 Version 1809. Given the absence of a linked patch at the time of this report, organizations should implement compensating controls such as restricting local access to trusted users only and employing strict access control policies. Use endpoint detection and response (EDR) solutions to monitor for suspicious privilege escalation attempts. Network segmentation can limit the spread of an attacker who gains local access. Organizations should also consider upgrading affected systems to a supported and patched version of Windows 10 or later, as newer versions are less likely to be vulnerable. Applying principle of least privilege (PoLP) to user accounts and regularly auditing local accounts can reduce the attack surface. Additionally, implementing application whitelisting and enhanced logging for Windows Shell activities can help detect and prevent exploitation attempts. Once Microsoft releases an official patch, organizations must apply it promptly to remediate the vulnerability.