CVE-2026-20868 is a heap-based buffer overflow vulnerability classified under CWE-122, affecting the Windows Routing and Remote Access Service (RRAS) component in Microsoft Windows 10 Version 1809 (build 10.0.17763.0). This vulnerability allows an unauthenticated attacker to remotely execute arbitrary code on the affected system by sending specially crafted network packets to the RRAS service. The flaw arises from improper handling of memory buffers in RRAS, leading to overflow conditions that can overwrite adjacent memory and enable code execution. The CVSS v3.1 base score is 8.8, indicating high severity, with attack vector network (AV:N), low attack complexity (AC:L), no privileges required (PR:N), but user interaction required (UI:R). The scope is unchanged (S:U), and the impact on confidentiality, integrity, and availability is high (C:H/I:H/A:H). Although no exploits are currently known in the wild, the vulnerability's characteristics make it a prime target for attackers seeking remote code execution capabilities without authentication. The vulnerability was reserved in December 2025 and published in January 2026, but no patches or mitigations have been linked yet. RRAS is commonly used for VPN and routing services, making this vulnerability particularly dangerous in environments where RRAS is exposed to untrusted networks.

For European organizations, the impact of CVE-2026-20868 can be severe. Successful exploitation allows attackers to gain remote code execution privileges without authentication, potentially leading to full system compromise. This threatens the confidentiality of sensitive data, the integrity of systems and applications, and the availability of critical network services. Organizations relying on RRAS for VPN or routing services may face disruptions, data breaches, or lateral movement by attackers within their networks. Critical infrastructure sectors such as energy, finance, healthcare, and government agencies are especially at risk due to their reliance on secure remote access. The vulnerability could facilitate ransomware deployment, espionage, or sabotage. The requirement for user interaction slightly reduces risk but does not eliminate it, as phishing or social engineering could trigger exploitation. The absence of known exploits currently provides a window for proactive defense, but the high severity score underscores the urgency of mitigation.

1. Immediately assess the use of RRAS in your environment; disable the service if it is not essential to reduce the attack surface. 2. Restrict network access to RRAS ports (typically TCP/UDP 1723 and GRE protocol 47) using firewalls and network segmentation to limit exposure to untrusted networks. 3. Implement strict access controls and monitoring on systems running Windows 10 Version 1809 with RRAS enabled. 4. Educate users about the risk of social engineering and user interaction required for exploitation to reduce successful attack likelihood. 5. Monitor network traffic for anomalous activity targeting RRAS services. 6. Apply security updates and patches from Microsoft as soon as they become available; track official advisories closely. 7. Consider upgrading affected systems to a supported Windows version with active security support and mitigations. 8. Employ endpoint detection and response (EDR) solutions to detect and respond to exploitation attempts. 9. Conduct regular vulnerability assessments and penetration testing focusing on remote access services. 10. Maintain robust backup and incident response plans to recover quickly in case of compromise.