CVE-2024-21420 is a high-severity vulnerability identified in Microsoft Windows 10 Version 1809, specifically affecting the Windows Defender Application Control (WDAC) OLE DB provider for SQL Server. The underlying issue is an integer overflow or wraparound (CWE-190) that can be triggered remotely, leading to a potential remote code execution (RCE) scenario. An integer overflow occurs when an arithmetic operation attempts to create a numeric value that is outside the range that can be represented with a given number of bits, causing unexpected behavior such as memory corruption. In this case, the vulnerability exists in the handling of data by the OLE DB provider, which is a component that facilitates communication between SQL Server and other applications. Exploiting this flaw requires no privileges (PR:N) but does require user interaction (UI:R), such as convincing a user to open a malicious file or connect to a malicious server. The attack vector is network-based (AV:N), meaning the attacker can exploit the vulnerability remotely over a network. The vulnerability impacts confidentiality, integrity, and availability (all rated high), allowing an attacker to execute arbitrary code with the privileges of the affected application or user, potentially leading to full system compromise. The CVSS 3.1 base score is 8.8, reflecting the high impact and relatively low complexity of exploitation. No known exploits are currently reported in the wild, but the vulnerability is publicly disclosed and should be considered a significant risk for affected systems. The affected version is Windows 10 Version 1809 (build 10.0.17763.0), which is an older release of Windows 10, but still in use in some environments. No official patch links were provided at the time of this report, indicating that mitigation may rely on workarounds or awaiting an official update from Microsoft.

For European organizations, this vulnerability poses a substantial risk, especially for those still operating legacy Windows 10 Version 1809 systems. The ability for remote code execution without requiring privileges means attackers can potentially compromise systems by tricking users into interacting with malicious content or servers. This could lead to data breaches, unauthorized access to sensitive information, disruption of business operations, and lateral movement within networks. Organizations in sectors such as finance, healthcare, government, and critical infrastructure are particularly at risk due to the sensitive nature of their data and the potential for significant operational impact. The high impact on confidentiality, integrity, and availability means that exploitation could result in theft or manipulation of data, installation of persistent malware, or denial of service conditions. The lack of known exploits in the wild currently provides a window for proactive mitigation, but the public disclosure increases the risk of rapid development of exploit code by threat actors. European organizations with compliance requirements such as GDPR must also consider the regulatory implications of a breach resulting from this vulnerability.

1. Immediate identification and inventory of all systems running Windows 10 Version 1809 within the organization to assess exposure. 2. Apply any available Microsoft security updates or patches as soon as they are released. Monitor Microsoft’s official security advisories and update channels closely. 3. If patches are not yet available, implement network-level protections such as firewall rules to restrict access to SQL Server and OLE DB provider services from untrusted networks. 4. Employ application whitelisting and endpoint protection solutions that can detect or block exploitation attempts targeting the OLE DB provider. 5. Educate users to avoid interacting with unsolicited or suspicious content that could trigger the vulnerability, reducing the risk posed by required user interaction. 6. Consider upgrading affected systems to a more recent and supported version of Windows 10 or Windows 11, which are less likely to be vulnerable. 7. Enable and monitor detailed logging and alerting for unusual activity related to SQL Server and OLE DB provider usage to detect potential exploitation attempts early. 8. Conduct penetration testing or vulnerability scanning focused on this CVE to validate the effectiveness of mitigations and identify any residual risk.