CVE-2025-47981 is a critical heap-based buffer overflow vulnerability identified in Microsoft Windows 10 Version 1809 (build 10.0.17763.0). The flaw exists within the implementation of the SPNEGO (Simple and Protected GSSAPI Negotiation Mechanism) Extended Negotiation protocol, which is used for negotiating authentication mechanisms over a network. This vulnerability allows an unauthenticated attacker to send specially crafted network packets to a vulnerable system, triggering a heap overflow condition. This overflow can corrupt memory, enabling the attacker to execute arbitrary code remotely without requiring any user interaction or prior authentication. The vulnerability is classified under CWE-122, indicating a heap-based buffer overflow, which is a common and dangerous class of memory corruption bugs. The CVSS v3.1 base score is 9.8, reflecting the high impact on confidentiality, integrity, and availability, combined with the ease of exploitation over the network without privileges or user interaction. Although no known exploits are currently reported in the wild, the critical nature and remote code execution capability make this vulnerability a significant threat. The absence of patch links suggests that a fix may not yet be publicly available or is pending release, increasing the urgency for organizations to monitor updates and apply mitigations promptly once available.

For European organizations, the impact of CVE-2025-47981 could be severe. Since Windows 10 Version 1809 is still in use in many enterprise environments, especially in legacy systems or where upgrade cycles are slow, vulnerable systems could be compromised remotely. Successful exploitation could lead to full system compromise, allowing attackers to steal sensitive data, disrupt business operations, deploy ransomware, or establish persistent footholds within networks. Critical infrastructure sectors such as finance, healthcare, government, and manufacturing, which often rely on Windows 10 endpoints, could face operational disruptions and data breaches. The vulnerability’s network-based attack vector means that attackers could target exposed systems directly or pivot through internal networks once initial access is gained. This elevates the risk of lateral movement and widespread compromise within organizational networks. Additionally, the lack of authentication and user interaction requirements lowers the barrier for attackers, increasing the likelihood of exploitation attempts. The potential for high-impact attacks makes this vulnerability a priority for European cybersecurity teams to address swiftly.

Given the absence of an official patch at the time of this report, European organizations should implement immediate compensating controls. These include: 1) Restricting network exposure of vulnerable Windows 10 Version 1809 systems by limiting inbound traffic to trusted sources and blocking unnecessary ports and protocols associated with SPNEGO negotiation. 2) Employing network-level intrusion detection and prevention systems (IDS/IPS) with updated signatures to detect and block suspicious SPNEGO negotiation attempts. 3) Applying strict network segmentation to isolate legacy Windows 10 systems from critical infrastructure and sensitive data stores. 4) Monitoring network traffic for anomalous authentication negotiation patterns indicative of exploitation attempts. 5) Accelerating plans to upgrade or replace Windows 10 Version 1809 systems with supported, patched versions of Windows. 6) Implementing application whitelisting and endpoint detection and response (EDR) solutions to detect and prevent execution of unauthorized code. 7) Preparing incident response plans specifically addressing remote code execution attacks targeting authentication protocols. Once Microsoft releases an official patch, organizations must prioritize rapid deployment across all affected systems to eliminate the vulnerability.