CVE-2025-21294 is a high-severity vulnerability affecting Microsoft Windows 10 Version 1809 (build 10.0.17763.0). It is categorized under CWE-591, which involves sensitive data storage in improperly locked memory. The vulnerability specifically relates to Microsoft Digest Authentication, a protocol used for HTTP authentication. The flaw allows remote code execution (RCE) without requiring any privileges or user interaction, meaning an unauthenticated attacker can exploit this vulnerability over the network. The CVSS 3.1 base score is 8.1, indicating a high impact on confidentiality, integrity, and availability. The attack vector is network-based (AV:N), but the attack complexity is high (AC:H), suggesting some conditions must be met for successful exploitation. The vulnerability is in the way sensitive data is stored in memory without proper locking mechanisms, potentially allowing attackers to execute arbitrary code remotely by exploiting weaknesses in the Digest Authentication implementation. No known exploits are currently reported in the wild, and no official patches have been linked yet, indicating that organizations should prioritize monitoring and mitigation. Given the nature of the vulnerability, it could be leveraged to compromise systems remotely, leading to full system takeover, data breaches, or disruption of services.

For European organizations, this vulnerability poses a significant risk, especially for those still operating legacy systems or Windows 10 Version 1809 in critical infrastructure, government, finance, healthcare, and industrial sectors. The ability for remote unauthenticated attackers to execute code could lead to widespread compromise of sensitive data and operational disruption. Confidentiality is at high risk due to exposure of sensitive data in memory, integrity is compromised through potential unauthorized code execution, and availability could be affected if attackers deploy ransomware or disrupt services. The lack of user interaction and privileges required makes this vulnerability particularly dangerous in automated attack scenarios or wormable exploits. European organizations with remote-facing services using Digest Authentication are especially vulnerable. The absence of patches increases the urgency for interim mitigations to prevent exploitation.

1. Immediate mitigation should include disabling Microsoft Digest Authentication on Windows 10 Version 1809 systems where feasible, especially on internet-facing services. 2. Employ network-level protections such as Web Application Firewalls (WAFs) and Intrusion Prevention Systems (IPS) configured to detect and block suspicious Digest Authentication traffic patterns. 3. Restrict network exposure of vulnerable systems by implementing strict firewall rules and network segmentation to limit access to trusted internal networks only. 4. Monitor network traffic and system logs for unusual authentication attempts or remote code execution indicators. 5. Upgrade affected systems to a supported and patched Windows version as soon as Microsoft releases a security update. 6. Apply principle of least privilege and ensure that critical systems are not running unnecessary services that use Digest Authentication. 7. Conduct regular vulnerability scanning and penetration testing focused on authentication mechanisms to identify and remediate weaknesses proactively.