Exchange 2019 CU12 brought several transformative capabilities to the server role: Exchange 2019 | Jaap Wesselius | Page 3
Historically, Exchange utilized BinaryFormatter serialization, a method that, while efficient, was prone to deserialization attacks—a common vector for remote code execution. CU12 introduced the capability to change the serialization mode to JsonFormatter . While this change was not enabled by default immediately upon installation, CU12 provided the necessary groundwork for administrators to switch to a more secure serialization method. This update was a direct response to the evolving threat landscape, forcing organizations to modernize their security posture. By prioritizing the mitigation of deserialization vulnerabilities, CU12 marked a turning point in the hardening of on-premises Exchange environments. exchange 2019 cu12
Technical Overview: Microsoft Exchange Server 2019 CU12 (KB5011156) This update was a direct response to the
Another critical feature introduced in CU12 was the capability for Hybrid Modern App Authentication (HMA). As organizations increasingly operate in a hybrid environment—maintaining on-premises mailboxes while utilizing cloud services—authentication methods have become a complex challenge. HMA allows on-premises clients to leverage OAuth for authentication against Exchange Online, enhancing security by moving away from legacy authentication protocols which are frequently targeted by phishing and password spray attacks. Exchange utilized BinaryFormatter serialization