CVE-2023-36050 is a deserialization of untrusted data vulnerability (CWE-502) identified in Microsoft Exchange Server 2019 Cumulative Update 12 (version 15.02.0). Deserialization vulnerabilities occur when untrusted input is deserialized by an application without proper validation, allowing attackers to manipulate the process to execute arbitrary code or perform unauthorized actions. In this case, the vulnerability enables an attacker with low privileges and network access (attack vector: adjacent network) to perform spoofing attacks against the Exchange server. The CVSS 3.1 base score is 8.0 (high), reflecting high impact on confidentiality, integrity, and availability, with low attack complexity and no user interaction required. The vulnerability does not require user interaction but does require some level of privileges (PR:L), which may be achievable through other means or insider threat scenarios. The scope is unchanged, meaning the vulnerability affects only the vulnerable component. Although no public exploit code or known active exploitation has been reported, the critical nature of Exchange servers as email infrastructure makes this vulnerability a significant concern. The lack of a patch link in the provided data suggests that organizations should monitor Microsoft advisories closely for updates and apply them promptly once available. The vulnerability was reserved in June 2023 and published in November 2023, indicating recent discovery and disclosure.

For European organizations, this vulnerability poses a serious threat due to the widespread use of Microsoft Exchange Server 2019 in enterprise environments, including government, finance, healthcare, and critical infrastructure sectors. Successful exploitation could lead to unauthorized access to sensitive emails, data exfiltration, disruption of email services, and potential lateral movement within networks. The high impact on confidentiality, integrity, and availability could result in significant operational disruption and data breaches, affecting compliance with GDPR and other data protection regulations. The requirement for low privileges and no user interaction lowers the barrier for attackers, increasing the risk of exploitation especially in environments with insufficient network segmentation or weak internal access controls. The absence of known exploits currently provides a window for proactive mitigation before active attacks emerge.

Organizations should immediately verify their Exchange Server 2019 version and apply the latest cumulative updates or security patches from Microsoft as soon as they become available. In the interim, network-level mitigations such as restricting access to Exchange services to trusted IP ranges, enforcing strict firewall rules, and implementing network segmentation can reduce exposure. Monitoring Exchange server logs for unusual deserialization activity or spoofing attempts is recommended. Employing application whitelisting and endpoint detection and response (EDR) solutions can help detect and block exploitation attempts. Additionally, reviewing and minimizing privileges assigned to users and service accounts interacting with Exchange servers will limit the potential for privilege escalation. Organizations should also ensure robust backup and incident response plans are in place to recover quickly in case of compromise.