CVE-2023-21674 is a use-after-free vulnerability classified under CWE-416 that exists within the Windows Advanced Local Procedure Call (ALPC) component in Microsoft Windows 10 Version 1809 (build 10.0.17763.0). ALPC is a core IPC (inter-process communication) mechanism used extensively within Windows for communication between user-mode and kernel-mode components. The vulnerability arises when the ALPC component improperly handles memory, leading to a use-after-free condition. This flaw can be exploited by a local attacker with limited privileges (low-level user) to execute arbitrary code in kernel mode, effectively elevating their privileges to SYSTEM level. The CVSS v3.1 score of 8.8 reflects high impact across confidentiality, integrity, and availability, with low attack complexity and no user interaction required. The scope is changed (S:C), meaning the vulnerability can affect resources beyond the initially compromised component. Although no public exploits have been reported, the vulnerability is critical due to the potential for complete system compromise. The vulnerability was reserved in December 2022 and published in January 2023. No official patch links were provided in the data, but Microsoft typically issues security updates for such vulnerabilities. This vulnerability is particularly relevant for organizations still running Windows 10 Version 1809, which is an older, out-of-support version, increasing risk due to lack of ongoing security updates.

For European organizations, the impact of CVE-2023-21674 can be severe. Successful exploitation allows attackers to gain SYSTEM-level privileges from a low-privileged local account, enabling full control over affected systems. This can lead to unauthorized access to sensitive data, disruption of critical services, and deployment of further malware or ransomware. The vulnerability compromises confidentiality, integrity, and availability of systems. Organizations in sectors such as finance, healthcare, government, and critical infrastructure are at heightened risk due to the potential for data breaches and operational disruption. Legacy systems running Windows 10 Version 1809 are particularly vulnerable, and the lack of patches increases exposure. The ease of exploitation without user interaction means that insider threats or malware with local access could leverage this vulnerability to escalate privileges rapidly. This elevates the risk of lateral movement within networks and persistent footholds by attackers.

1. Upgrade or patch: The primary mitigation is to apply the official Microsoft security update addressing CVE-2023-21674. If no patch is available for Windows 10 Version 1809, organizations should upgrade to a supported Windows version that receives security updates. 2. Restrict local access: Limit local user accounts and restrict administrative privileges to reduce the attack surface. 3. Endpoint protection: Deploy advanced endpoint detection and response (EDR) solutions capable of detecting suspicious privilege escalation attempts and anomalous ALPC activity. 4. Application whitelisting: Implement application control policies to prevent unauthorized code execution. 5. Network segmentation: Isolate critical systems to limit lateral movement if exploitation occurs. 6. Monitoring and auditing: Enable detailed logging of privilege escalation events and monitor for unusual behavior indicative of exploitation attempts. 7. User awareness: Train users to recognize and report suspicious activity, especially in environments where local access might be compromised. 8. Incident response readiness: Prepare and test incident response plans to quickly contain and remediate potential exploitation.