CVE-2025-49691 is a high-severity heap-based buffer overflow vulnerability identified in Microsoft Windows 10 Version 1809 (build 10.0.17763.0), specifically within the Windows Media component. This vulnerability is classified under CWE-122, indicating improper handling of memory buffers leading to overflow conditions on the heap. An attacker exploiting this flaw can cause a buffer overflow by sending specially crafted data to the vulnerable Windows Media processing functionality. The overflow can overwrite adjacent memory, potentially allowing the attacker to execute arbitrary code with the privileges of the affected process. The attack vector is over an adjacent network, meaning the attacker does not require local access but must be able to send data over a network segment directly reachable by the target system. No privileges are required to initiate the attack, but user interaction is necessary, likely involving the user processing or opening malicious media content. The vulnerability impacts confidentiality, integrity, and availability, as successful exploitation can lead to full system compromise, data theft, or denial of service. The CVSS v3.1 base score is 8.0, reflecting high severity with attack vector as adjacent network (AV:A), low attack complexity (AC:L), no privileges required (PR:N), and user interaction required (UI:R). The scope is unchanged (S:U), but the impact on confidentiality, integrity, and availability is high (C:H/I:H/A:H). No known exploits are currently reported in the wild, and no official patches have been linked yet. However, given the nature of the vulnerability and its potential impact, it represents a significant risk to affected systems.

For European organizations, this vulnerability poses a substantial risk, especially for those still operating Windows 10 Version 1809 in their environments. The ability to execute arbitrary code remotely over an adjacent network can lead to widespread compromise of enterprise systems, including unauthorized data access, disruption of business operations, and potential lateral movement within internal networks. Critical infrastructure sectors, government agencies, and enterprises relying on legacy Windows 10 systems are particularly vulnerable. The requirement for user interaction may limit mass exploitation but targeted phishing or social engineering campaigns could facilitate attacks. The high impact on confidentiality, integrity, and availability means sensitive data could be exfiltrated or systems rendered inoperable, leading to regulatory compliance issues under GDPR and potential financial and reputational damage. Additionally, the lack of available patches increases the urgency for mitigation, as attackers may develop exploits once the vulnerability becomes widely known.

European organizations should immediately identify and inventory all systems running Windows 10 Version 1809 to assess exposure. Since no official patch is currently available, organizations should implement network segmentation to limit exposure to adjacent network attacks, particularly isolating vulnerable systems from untrusted network segments. Employ strict network access controls and monitoring to detect anomalous media file transfers or suspicious network activity targeting Windows Media services. User awareness training should be enhanced to reduce the risk of social engineering that could trigger user interaction with malicious media content. Organizations should consider disabling or restricting Windows Media components where feasible or using application whitelisting to prevent execution of unauthorized media processing applications. Deploy endpoint detection and response (EDR) solutions capable of identifying exploitation attempts related to heap-based buffer overflows. Finally, plan and prioritize upgrading affected systems to supported Windows versions with security patches as soon as they become available to eliminate the vulnerability.