CVE-2025-29840 is a high-severity stack-based buffer overflow vulnerability identified in the Windows Media component of Microsoft Windows 10 Version 1809 (build 10.0.17763.0). This vulnerability arises from improper handling of input data within the Windows Media processing functionality, allowing an attacker to overflow a buffer on the stack. Exploitation of this vulnerability enables an unauthorized attacker to execute arbitrary code remotely over a network without requiring any prior authentication, although user interaction is required. The vulnerability is classified under CWE-121, which pertains to stack-based buffer overflows, a common and dangerous class of memory corruption issues. The CVSS 3.1 base score of 8.8 reflects the high impact on confidentiality, integrity, and availability, with an attack vector that is network-based and low attack complexity. Successful exploitation could allow an attacker to gain control over the affected system, potentially leading to full system compromise, data theft, or disruption of services. Despite the severity, as of the publication date (May 13, 2025), no known exploits have been observed in the wild. No official patches or mitigation links have been provided yet, indicating that affected organizations must prioritize monitoring and prepare for imminent patch deployment. The vulnerability affects Windows 10 Version 1809, an older but still in-use version of Windows 10, which may be present in legacy systems or environments with delayed upgrade cycles.

For European organizations, this vulnerability poses a significant risk, especially for those still operating Windows 10 Version 1809 in production environments. The ability for an attacker to remotely execute code without authentication means that critical infrastructure, enterprise networks, and public sector systems could be compromised remotely, leading to data breaches, ransomware deployment, or disruption of essential services. Confidentiality is at high risk due to potential data exfiltration, integrity can be compromised by unauthorized code execution altering system behavior, and availability may be affected if attackers deploy destructive payloads or cause system crashes. The requirement for user interaction slightly reduces the risk but does not eliminate it, as social engineering or phishing campaigns could be used to trigger the exploit. European organizations with strict data protection regulations (e.g., GDPR) face additional compliance risks if this vulnerability leads to data breaches. The lack of known exploits in the wild provides a window for proactive defense, but the high CVSS score demands urgent attention to prevent exploitation.

1. Immediate inventory and identification of all systems running Windows 10 Version 1809 to understand exposure. 2. Prioritize upgrading or migrating affected systems to a supported and patched version of Windows 10 or later, as Windows 10 Version 1809 is an older release with limited support. 3. Until patches are available, implement network-level protections such as blocking or restricting access to Windows Media services or related network ports from untrusted networks. 4. Employ endpoint detection and response (EDR) solutions to monitor for anomalous behavior indicative of exploitation attempts, including unexpected process creations or memory corruption indicators. 5. Educate users about the risks of interacting with unsolicited media files or links, as user interaction is required for exploitation. 6. Monitor threat intelligence feeds and Microsoft security advisories closely for the release of official patches or workarounds. 7. Apply application whitelisting and restrict execution privileges to limit the impact of potential code execution. 8. Conduct regular backups and ensure recovery plans are tested to mitigate potential ransomware or destructive attacks stemming from exploitation.