CVE-2026-20829 is an out-of-bounds read vulnerability classified under CWE-125 affecting the Trusted Platform Module (TPM) implementation in Microsoft Windows 10 Version 1809 (build 17763.0). The TPM is a hardware-based security component used for secure cryptographic operations and key storage. This vulnerability allows an authorized attacker with local access and low privileges to read memory outside the intended bounds within the TPM software interface. Such an out-of-bounds read can lead to disclosure of sensitive information stored or processed by the TPM, such as cryptographic keys, credentials, or other protected data. The vulnerability does not allow code execution or modification of data, thus integrity and availability remain unaffected. The CVSS v3.1 base score is 5.5 (medium), reflecting the local attack vector (AV:L), low complexity (AC:L), required privileges (PR:L), no user interaction (UI:N), and high confidentiality impact (C:H). No known exploits have been reported in the wild, and no patches are currently linked, indicating that mitigation relies on vendor updates and access controls. The vulnerability is specific to Windows 10 Version 1809, an older release that may still be present in enterprise environments. This flaw highlights the risks associated with legacy systems and the importance of TPM security in protecting cryptographic assets.

For European organizations, the primary impact of CVE-2026-20829 is the potential unauthorized disclosure of sensitive TPM-protected information, which could include cryptographic keys used for disk encryption, authentication, or secure boot processes. This leakage could facilitate further attacks such as credential theft or bypassing security controls that rely on TPM integrity. Although the vulnerability does not allow remote exploitation or system compromise, the requirement for local access means that insider threats or attackers who have gained limited access could leverage this flaw. Organizations in sectors with high security requirements—such as finance, government, healthcare, and critical infrastructure—may face increased risk if legacy Windows 10 1809 systems remain in use. The confidentiality breach could undermine trust in secure computing environments and complicate compliance with data protection regulations like GDPR. However, since integrity and availability are not affected, the immediate operational impact is limited. The absence of known exploits reduces the urgency but does not eliminate the risk, especially as attackers may develop techniques over time.

1. Prioritize upgrading or patching Windows 10 systems running Version 1809 to a supported and updated version where this vulnerability is addressed. 2. Restrict local access to systems with TPM to trusted and authorized personnel only, employing strict access controls and monitoring. 3. Implement endpoint security solutions that can detect and prevent unauthorized local privilege escalation or suspicious activity. 4. Regularly audit and inventory systems to identify legacy Windows 10 1809 deployments and plan for their timely decommissioning or upgrade. 5. Use hardware-based security features and firmware TPM updates if available, as they may provide additional protection layers. 6. Employ network segmentation to limit lateral movement and reduce the risk of attackers gaining local access to vulnerable systems. 7. Monitor security advisories from Microsoft for patches or workarounds related to this CVE and apply them promptly. 8. Educate users and administrators about the risks of local access vulnerabilities and enforce strong physical security controls in sensitive environments.