CVE-2025-27487 is a high-severity heap-based buffer overflow vulnerability identified in the Microsoft Windows App Client for Windows Desktop, specifically version 1.00. This vulnerability is classified under CWE-122, which pertains to improper handling of memory buffers leading to overflow conditions on the heap. The flaw exists within the Remote Desktop Client component, which is responsible for enabling remote connections to Windows desktops. An authorized attacker with network access and limited privileges (PR:L) can exploit this vulnerability by sending specially crafted data to the Remote Desktop Client, triggering a heap overflow. This overflow can corrupt memory, allowing the attacker to execute arbitrary code remotely with the privileges of the targeted process. The CVSS v3.1 base score is 8.0, reflecting a high severity due to the combination of network attack vector (AV:N), low attack complexity (AC:L), and the ability to impact confidentiality, integrity, and availability (all rated high). User interaction is required (UI:R), meaning the victim must initiate or accept a remote desktop session for exploitation to occur. The vulnerability scope is unchanged (S:U), indicating the exploit affects resources within the same security scope. Although no known exploits are currently reported in the wild, the vulnerability is publicly disclosed and considered critical for organizations relying on Remote Desktop services. The lack of available patches at the time of publication increases the urgency for mitigation. Given the widespread use of Microsoft Windows and Remote Desktop Protocol (RDP) in enterprise environments, this vulnerability poses a significant risk for remote code execution attacks that could lead to full system compromise or lateral movement within networks.

For European organizations, this vulnerability presents a substantial risk due to the extensive adoption of Microsoft Windows and Remote Desktop services across public and private sectors, including government agencies, financial institutions, healthcare providers, and critical infrastructure operators. Successful exploitation could lead to unauthorized remote code execution, resulting in data breaches, disruption of services, and potential ransomware deployment. The high impact on confidentiality, integrity, and availability could compromise sensitive personal data protected under GDPR, leading to regulatory penalties and reputational damage. Additionally, the requirement for user interaction may limit automated exploitation but does not eliminate risk, especially in environments where remote desktop sessions are frequently initiated by users or administrators. The vulnerability could be leveraged in targeted attacks against high-value European targets, potentially affecting cross-border operations and critical services. The absence of known exploits in the wild currently provides a window for proactive defense, but the high severity score necessitates immediate attention to prevent future exploitation.

1. Immediately review and restrict Remote Desktop access to essential personnel only, employing network-level authentication and strong access controls. 2. Implement multi-factor authentication (MFA) for all remote desktop sessions to reduce the risk of unauthorized access. 3. Monitor network traffic for unusual Remote Desktop Protocol (RDP) activity, including unexpected session initiations or anomalous data patterns indicative of exploitation attempts. 4. Employ endpoint detection and response (EDR) solutions capable of detecting heap-based memory corruption and suspicious process behaviors related to RDP clients. 5. Until an official patch is released, consider disabling or limiting the use of the affected Windows App Client version 1.00 where feasible, or use alternative remote access solutions with a strong security posture. 6. Educate users about the risks of accepting unsolicited or unexpected remote desktop connection requests to mitigate the user interaction requirement. 7. Maintain up-to-date backups and incident response plans to quickly recover from potential compromises. 8. Regularly check for and apply security updates from Microsoft as soon as patches addressing CVE-2025-27487 become available.