CVE-2026-20929 is a vulnerability classified under CWE-284 (Improper Access Control) affecting the HTTP.sys component in Microsoft Windows 10 Version 1809 (build 10.0.17763.0). HTTP.sys is a kernel-mode device driver that handles HTTP requests for Windows services. The flaw arises from improper access control mechanisms within HTTP.sys, allowing an attacker who is authorized on the network but with low privileges to escalate their privileges remotely. The attacker does not require user interaction to exploit this vulnerability, increasing its risk profile. The CVSS v3.1 base score is 7.5, indicating high severity, with the vector string AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H, meaning the attack is network-based, requires high attack complexity, low privileges, no user interaction, and impacts confidentiality, integrity, and availability. No public exploits or patches are currently available, but the vulnerability is published and recognized by Microsoft. This vulnerability could allow attackers to gain SYSTEM-level privileges, potentially leading to full system compromise, data theft, or disruption of services. Since Windows 10 Version 1809 is still in use in many enterprise environments, especially where legacy systems persist, this vulnerability represents a significant threat vector.

For European organizations, the impact of CVE-2026-20929 can be substantial. Successful exploitation could lead to unauthorized privilege escalation, enabling attackers to execute arbitrary code with SYSTEM privileges, access sensitive data, disrupt critical services, or deploy ransomware. Organizations relying on Windows 10 Version 1809, particularly in sectors such as finance, healthcare, government, and critical infrastructure, face increased risk. The network-based attack vector means that attackers can exploit the vulnerability remotely, potentially bypassing perimeter defenses if HTTP.sys services are exposed or accessible internally. This could lead to lateral movement within corporate networks, increasing the scope of compromise. The lack of user interaction requirement further elevates the risk, as automated attacks or worm-like propagation could be possible if combined with other vulnerabilities. The absence of known exploits in the wild currently provides a window for proactive mitigation, but the high severity score underscores the urgency for remediation.

1. Apply official security patches from Microsoft as soon as they become available for Windows 10 Version 1809 systems. 2. Restrict network access to HTTP.sys services by implementing strict firewall rules, limiting exposure to trusted networks only. 3. Employ network segmentation to isolate vulnerable systems and reduce the attack surface. 4. Monitor network traffic for unusual HTTP.sys activity or privilege escalation attempts using advanced intrusion detection systems. 5. Conduct regular vulnerability assessments and penetration testing focused on legacy Windows environments. 6. Consider upgrading affected systems to supported Windows versions with ongoing security updates to reduce exposure to legacy vulnerabilities. 7. Implement strict access controls and least privilege principles to minimize the impact of potential privilege escalations. 8. Maintain comprehensive logging and alerting to detect exploitation attempts promptly.