CVE-2026-20828 is a security vulnerability classified under CWE-125 (Out-of-bounds Read) affecting the Internet Connection Sharing (ICS) component in Microsoft Windows 10 Version 1809 (build 10.0.17763.0). The vulnerability arises from improper bounds checking in ICS, which allows an attacker with physical access to the affected system to read memory outside the intended buffer boundaries. This out-of-bounds read can lead to unauthorized disclosure of sensitive information stored in adjacent memory areas. The attack vector requires physical access (AV:P), does not require privileges (PR:N), nor user interaction (UI:N), and impacts confidentiality (C:H) without affecting integrity or availability. The vulnerability is rated medium severity with a CVSS 3.1 base score of 4.6. No public exploits or patches are currently available, but the vulnerability is officially published and recognized. The flaw could be exploited by attackers who gain physical access to devices running Windows 10 1809, potentially leaking sensitive data that could facilitate further attacks or reconnaissance. Since ICS is often used in network sharing scenarios, compromised devices could expose network configuration or credentials. The vulnerability's scope is limited to systems running the specific Windows 10 version and ICS enabled, reducing widespread impact but posing risks in environments relying on legacy systems or where physical security is weak.

For European organizations, the primary impact of CVE-2026-20828 is unauthorized disclosure of sensitive information due to out-of-bounds memory reads in Windows ICS on legacy Windows 10 1809 systems. This could lead to leakage of network configuration details, credentials, or other sensitive data, potentially enabling lateral movement or further exploitation within corporate networks. Critical infrastructure sectors such as energy, manufacturing, and transportation that may still operate legacy Windows 10 systems with ICS enabled are particularly vulnerable. The requirement for physical access limits remote exploitation but raises concerns for environments with shared or poorly secured physical access, such as offices, data centers, or industrial sites. The vulnerability does not affect system integrity or availability directly but compromises confidentiality, which can have cascading effects on organizational security posture. Additionally, the lack of patches increases risk until mitigations are applied. European organizations must consider this vulnerability in their risk assessments, especially those with legacy Windows deployments and physical security challenges.

1. Inventory and identify all systems running Windows 10 Version 1809 (build 10.0.17763.0) and assess ICS usage on these devices. 2. Disable Internet Connection Sharing (ICS) on all systems where it is not explicitly required to reduce the attack surface. 3. Restrict physical access to devices running vulnerable Windows versions, especially in sensitive or critical environments, to prevent unauthorized physical attacks. 4. Implement strict physical security controls such as locked server rooms, badge access, and surveillance to limit attacker proximity. 5. Monitor network and system logs for unusual ICS activity or memory access patterns that could indicate exploitation attempts. 6. Prepare for patch deployment by tracking Microsoft updates and applying security patches promptly once available. 7. Consider upgrading affected systems to supported Windows versions with active security updates to eliminate exposure to this and similar vulnerabilities. 8. Educate IT and security staff about this vulnerability and the importance of physical security and ICS management. 9. Use endpoint detection and response (EDR) tools to detect anomalous behavior related to ICS or memory access. 10. For critical environments, consider network segmentation to isolate legacy systems and limit potential damage from information disclosure.