CVE-2024-20662 is a medium-severity vulnerability affecting Microsoft Windows Server 2019 (specifically version 10.0.17763.0). It is classified under CWE-843, which corresponds to 'Access of Resource Using Incompatible Type,' commonly known as a type confusion vulnerability. This flaw exists within the Windows Online Certificate Status Protocol (OCSP) implementation. OCSP is a protocol used to obtain the revocation status of X.509 digital certificates, which is critical for validating the trustworthiness of certificates in secure communications. The vulnerability allows an attacker with high privileges (PR:H) to exploit a type confusion error, potentially leading to unauthorized disclosure of sensitive information related to certificate status. The CVSS v3.1 base score is 4.9, indicating a medium severity level. The vector string (AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:N/A:N) shows that the attack can be performed remotely over the network with low attack complexity but requires high privileges and no user interaction. The impact is primarily on confidentiality, with no effect on integrity or availability. No known exploits are currently in the wild, and no patches have been linked yet, though the vulnerability is publicly disclosed and tracked by CISA. The vulnerability could allow an attacker to access sensitive certificate status information, which might be leveraged for further attacks or reconnaissance within an enterprise environment. Since the vulnerability requires high privileges, it is likely exploitable only by insiders or through chained exploits that elevate privileges first.

For European organizations, the confidentiality breach of certificate status information could undermine trust in internal and external secure communications, especially in sectors relying heavily on PKI infrastructure such as finance, government, healthcare, and critical infrastructure. Disclosure of OCSP information might enable attackers to infer certificate usage patterns or identify revoked certificates, potentially facilitating man-in-the-middle attacks or bypassing security controls that rely on certificate validation. While the vulnerability does not directly impact system integrity or availability, the leakage of sensitive certificate data could have cascading effects on secure communications and compliance with data protection regulations like GDPR. Organizations using Windows Server 2019 in their certificate validation infrastructure are at risk, particularly if attackers can gain high-level access to these systems. The lack of known exploits reduces immediate risk, but the public disclosure means threat actors could develop exploits over time.

Given the absence of an official patch link, European organizations should implement compensating controls immediately. These include restricting administrative access to Windows Server 2019 systems running OCSP services, enforcing strict network segmentation to limit exposure of these servers, and monitoring for unusual access patterns or privilege escalations. Organizations should ensure that all Windows Server 2019 instances are updated with the latest cumulative updates from Microsoft as they become available, as these often include security fixes. Additionally, auditing and hardening the certificate infrastructure, including OCSP responders, is critical. Employing network-level protections such as firewalls and intrusion detection systems to monitor OCSP traffic can help detect anomalous behavior. Organizations should also consider deploying alternative certificate status checking mechanisms temporarily if feasible. Finally, maintaining a robust incident response plan to quickly address any signs of exploitation is recommended.