CVE-2024-26237 is a high-severity elevation of privilege vulnerability affecting Microsoft Windows 10 Version 1809 (build 10.0.17763.0). The vulnerability is classified as a Use After Free (CWE-416) issue within the Windows Defender Credential Guard component. Use After Free vulnerabilities occur when a program continues to use a pointer after the memory it points to has been freed, potentially leading to arbitrary code execution or escalation of privileges. In this case, the flaw allows an attacker with limited privileges (low-level privileges) to escalate their privileges to higher levels without requiring user interaction. The CVSS 3.1 base score is 7.8, reflecting high impact on confidentiality, integrity, and availability. The attack vector is local (AV:L), meaning the attacker must have local access to the system, and the attack complexity is low (AC:L), indicating that exploitation does not require sophisticated conditions. Privileges required are low (PR:L), and no user interaction is needed (UI:N). The vulnerability affects Windows Defender Credential Guard, a security feature designed to protect credentials and secrets from compromise by isolating them in a secure environment. Exploiting this vulnerability could allow an attacker to bypass these protections, potentially gaining access to sensitive credential information or executing code with elevated privileges. No known exploits are currently reported in the wild, and no patches have been linked yet, indicating that mitigation may rely on vendor updates once available. The vulnerability was published on April 9, 2024, and was reserved in mid-February 2024. Given the critical role of Credential Guard in enterprise security, this vulnerability represents a significant risk to affected systems still running this older Windows 10 version, which is no longer the latest but remains in use in some environments due to legacy application dependencies or delayed upgrade cycles.

For European organizations, the impact of CVE-2024-26237 could be substantial, especially in sectors relying on legacy Windows 10 Version 1809 deployments. Successful exploitation allows attackers with local access to escalate privileges, potentially leading to full system compromise. This could result in unauthorized access to sensitive data, including credentials protected by Credential Guard, undermining identity and access management controls. The compromise of Credential Guard could facilitate lateral movement within networks, increasing the risk of data breaches, ransomware deployment, or espionage activities. Critical infrastructure, government agencies, financial institutions, and healthcare providers in Europe that maintain legacy Windows 10 systems are particularly at risk. The vulnerability's local attack vector means that initial access must be obtained, possibly through phishing, physical access, or other means, but once inside, attackers can leverage this flaw to deepen their foothold. The lack of known exploits in the wild currently provides a window for proactive mitigation, but the high severity score and potential impact on confidentiality, integrity, and availability necessitate urgent attention.

1. Immediate prioritization of patch management: Although no patch links are currently provided, organizations should monitor Microsoft’s official security advisories and deploy updates as soon as patches become available. 2. Restrict local access: Limit the number of users with local access to systems running Windows 10 Version 1809. Implement strict access controls and use endpoint protection to detect and prevent unauthorized access attempts. 3. Upgrade legacy systems: Plan and execute upgrades from Windows 10 Version 1809 to supported, up-to-date Windows versions that include security improvements and patches for known vulnerabilities. 4. Enhance monitoring and detection: Deploy advanced endpoint detection and response (EDR) tools capable of identifying suspicious privilege escalation attempts and anomalous behavior related to Credential Guard. 5. Harden Credential Guard configurations: Review and enforce best practices for Credential Guard deployment, including ensuring it is enabled and properly configured to minimize attack surface. 6. Implement network segmentation: Limit lateral movement opportunities by segmenting networks and restricting communication between critical systems and user workstations. 7. Conduct user training: Educate users on the risks of local access exploitation vectors such as phishing or physical access to devices, reducing the likelihood of initial compromise. 8. Use multi-factor authentication (MFA): Where possible, enforce MFA to reduce the impact of credential theft or misuse following privilege escalation.