CVE-2025-26674 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, classified under CWE-122, allows an authorized attacker with local access and low privileges (PR:L) to execute arbitrary code on the affected system without requiring user interaction (UI:N). The flaw arises from improper handling of memory buffers in Windows Media, leading to potential overwriting of heap memory. Exploitation could result in full compromise of confidentiality, integrity, and availability of the system, as the attacker can execute code with the privileges of the logged-in user. The CVSS v3.1 base score is 7.8, reflecting high severity due to the combination of local attack vector, low complexity, and significant impact on system security. No known exploits are currently reported in the wild, and no patches have been linked yet, indicating that mitigation may rely on workarounds or system hardening until an official update is released. The vulnerability does not require user interaction, increasing the risk in environments where local access is possible, such as shared workstations or multi-user systems. Given that Windows 10 Version 1809 is an older release, many organizations may have already migrated to newer versions; however, legacy systems still running this version remain at risk. The lack of remote exploitation capability limits the attack surface to local attackers, but the potential for privilege escalation or lateral movement within an organization remains significant.

For European organizations, this vulnerability poses a substantial risk particularly to those maintaining legacy Windows 10 Version 1809 systems, which may be prevalent in industrial, governmental, or critical infrastructure environments where system upgrades are slower. Successful exploitation could lead to unauthorized code execution, enabling attackers to steal sensitive data, disrupt operations, or deploy ransomware and other malware. The high impact on confidentiality, integrity, and availability could result in data breaches, operational downtime, and regulatory non-compliance under GDPR and other data protection laws. The local attack vector means insider threats or attackers gaining physical or remote desktop access could leverage this vulnerability to escalate privileges or move laterally within networks. Organizations with shared user environments or remote access solutions that allow local code execution are particularly vulnerable. The absence of known exploits currently provides a window for proactive mitigation, but the lack of patches necessitates immediate attention to reduce exposure.

European organizations should prioritize identifying and inventorying all systems running Windows 10 Version 1809. Until an official patch is released, implement strict access controls to limit local user privileges and restrict physical and remote access to trusted personnel only. Employ application whitelisting and endpoint detection and response (EDR) solutions to monitor for anomalous behavior indicative of exploitation attempts. Disable or restrict Windows Media components where feasible, or use software restriction policies to limit execution of untrusted media files. Regularly audit and tighten group policies to prevent unauthorized software execution. Consider network segmentation to isolate legacy systems and reduce lateral movement opportunities. Additionally, organizations should prepare for rapid deployment of patches once available and maintain up-to-date backups to enable recovery from potential compromise. User education on the risks of local access and enforcing strong authentication mechanisms can further reduce exploitation likelihood.