CVE-2025-27481 is a high-severity stack-based buffer overflow vulnerability identified in the Windows Telephony Service component of Microsoft Windows 10 Version 1809 (build 10.0.17763.0). This vulnerability, classified under CWE-121, allows an unauthorized attacker to execute arbitrary code remotely over a network without requiring prior authentication, although user interaction is necessary to trigger the exploit. The vulnerability arises from improper handling of input data within the Telephony Service, leading to a buffer overflow on the stack. Exploitation of this flaw can result in complete compromise of the affected system, granting attackers the ability to execute code with system-level privileges, thereby impacting confidentiality, integrity, and availability. The CVSS v3.1 base score of 8.8 reflects the high impact and relatively low complexity of exploitation, with no privileges required and low attack complexity. The scope of the vulnerability is unchanged, meaning the impact is confined to the vulnerable component and system. Although no known exploits have been reported in the wild as of the publication date (April 8, 2025), the critical nature of the flaw and the widespread deployment of Windows 10 Version 1809 make it a significant security concern. The absence of available patches at the time of reporting increases the urgency for organizations to implement interim mitigations and monitor for updates from Microsoft.

For European organizations, the impact of CVE-2025-27481 could be severe, especially for those still operating legacy systems running Windows 10 Version 1809. Successful exploitation could lead to unauthorized remote code execution, enabling attackers to gain full control over affected machines. This could result in data breaches, disruption of business operations, deployment of ransomware, or lateral movement within corporate networks. Critical sectors such as finance, healthcare, government, and telecommunications are particularly at risk due to the sensitive nature of their data and services. The vulnerability's network-based attack vector increases the risk of widespread exploitation across organizational perimeters if exposed to untrusted networks. Additionally, the requirement for user interaction may limit automated exploitation but does not eliminate risk, as phishing or social engineering campaigns could be leveraged to trigger the vulnerability. The lack of known exploits currently provides a window for proactive defense, but organizations must act swiftly to prevent potential future attacks.

Given the absence of an official patch at the time of disclosure, European organizations should implement the following specific mitigations: 1) Disable or restrict the Windows Telephony Service where it is not essential to business operations, reducing the attack surface. 2) Employ network-level controls such as firewall rules to block inbound traffic to ports and protocols associated with the Telephony Service, especially from untrusted networks. 3) Enhance endpoint protection by deploying advanced intrusion prevention systems (IPS) and endpoint detection and response (EDR) solutions capable of detecting anomalous behavior related to buffer overflow exploitation attempts. 4) Conduct targeted user awareness training to reduce the risk of successful social engineering or phishing attacks that could facilitate user interaction required for exploitation. 5) Monitor network and system logs for unusual activity indicative of exploitation attempts. 6) Prioritize upgrading or migrating systems from Windows 10 Version 1809 to supported, patched versions of Windows as soon as patches become available. 7) Maintain an up-to-date inventory of affected systems to ensure comprehensive coverage of mitigation efforts.