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 and is critical for web server functionality and other network services. The flaw allows an attacker who already has some level of authorized access with low privileges (PR:L) to remotely elevate their privileges over the network (AV:N), without requiring user interaction (UI:N). The vulnerability arises due to improper enforcement of access control policies within HTTP.sys, enabling privilege escalation that compromises confidentiality, integrity, and availability of the system. The CVSS v3.1 score is 7.5 (high), reflecting the network attack vector, the need for low privileges, and the significant impact on system security. Although no exploits are currently known in the wild, the vulnerability's characteristics make it a serious threat, especially in environments where Windows 10 Version 1809 remains in use. The lack of available patches at the time of publication increases the urgency for organizations to implement interim mitigations and prepare for updates. This vulnerability could be exploited to execute arbitrary code with elevated privileges or disrupt critical services relying on HTTP.sys, potentially affecting enterprise applications and infrastructure.

For European organizations, the impact of CVE-2026-20929 is considerable, particularly for those still operating Windows 10 Version 1809 in enterprise environments. Successful exploitation could lead to unauthorized privilege escalation, allowing attackers to gain administrative control over affected systems remotely. This could result in data breaches, unauthorized data modification, or service disruptions impacting business continuity. Critical sectors such as finance, healthcare, government, and industrial control systems that rely on Windows 10 1809 for legacy applications or infrastructure are at heightened risk. The network-based attack vector means that attackers do not need physical access, increasing the threat surface. Additionally, the absence of known exploits currently provides a window for proactive defense, but also means organizations must be vigilant for emerging threats. The compromise of confidentiality, integrity, and availability could lead to regulatory non-compliance under GDPR and other European data protection laws, with potential legal and financial repercussions.

Since no patches were available at the time of this vulnerability's disclosure, European organizations should implement the following specific mitigations: 1) Restrict network access to services relying on HTTP.sys by using firewalls and network segmentation to limit exposure to trusted hosts only. 2) Employ strict access control policies to minimize the number of users with low privileges who can access vulnerable systems remotely. 3) Monitor network traffic and system logs for unusual privilege escalation attempts or anomalous HTTP.sys activity. 4) Where feasible, upgrade affected systems to a later, supported Windows version that includes security fixes. 5) Apply any out-of-band security updates or workarounds released by Microsoft promptly once available. 6) Conduct thorough vulnerability assessments and penetration testing focused on HTTP.sys to identify potential exploitation paths. 7) Educate IT and security teams about this vulnerability to ensure rapid detection and response. These targeted actions go beyond generic advice by focusing on reducing attack surface, enhancing monitoring, and prioritizing system upgrades.