CVE-2025-29833 is a high-severity vulnerability identified as a Time-of-check Time-of-use (TOCTOU) race condition (CWE-367) affecting Microsoft Windows 10 Version 1809, specifically build 10.0.17763.0. The flaw exists within the Windows Virtual Machine Bus component, which is responsible for facilitating communication between the host and virtual machines. A TOCTOU race condition occurs when a system checks a condition and then uses the result of that check at a later time, during which the state may have changed, leading to inconsistent or insecure behavior. In this case, the race condition allows an unauthorized attacker to execute code locally by exploiting the timing window between the check and use operations. The vulnerability requires local access (attack vector: local), has high attack complexity, does not require privileges, but does require user interaction. The scope is changed, meaning the vulnerability can affect resources beyond the initially vulnerable component. The impact on confidentiality, integrity, and availability is high, indicating that successful exploitation can lead to full system compromise. No known exploits are currently reported in the wild, and no patches have been linked yet. The vulnerability was published on May 13, 2025, and was reserved on March 11, 2025. 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. The vulnerability's exploitation could allow attackers to bypass security controls and execute arbitrary code, potentially leading to privilege escalation or persistent compromise within affected environments.

For European organizations, this vulnerability poses a significant risk, especially for those still operating legacy systems running Windows 10 Version 1809. The ability to execute code locally without requiring privileges means that any user with local access, including potentially malicious insiders or users tricked into interaction, could exploit this flaw to escalate privileges or deploy malware. This could lead to data breaches, disruption of critical services, or lateral movement within networks. Industries with high reliance on virtualized environments, such as financial services, manufacturing, and government agencies, may face increased risk due to the involvement of the Virtual Machine Bus component. The high impact on confidentiality, integrity, and availability could result in severe operational disruptions and data loss. Additionally, the changed scope indicates that the vulnerability could affect other system components beyond the initial target, amplifying the potential damage. Organizations in Europe with strict data protection regulations like GDPR must be particularly vigilant, as exploitation could lead to regulatory penalties and reputational damage.

Given the absence of an official patch at this time, European organizations should take immediate steps to mitigate risk. First, identify and inventory all systems running Windows 10 Version 1809 and prioritize their upgrade to a supported and patched Windows version. If upgrading is not immediately feasible, restrict local access to affected systems by enforcing strict access controls and monitoring. Employ application whitelisting and endpoint detection and response (EDR) solutions to detect anomalous behavior indicative of exploitation attempts. Disable or limit the use of virtual machine features that rely on the Windows Virtual Machine Bus where possible, or isolate virtualized environments to reduce attack surface. Educate users about the risks of interacting with untrusted content or executing unknown applications, as user interaction is required for exploitation. Monitor security advisories from Microsoft closely for the release of patches or workarounds. Finally, implement robust logging and incident response plans to quickly identify and respond to any exploitation attempts.