Unit 42 stopped monitoring this threat and updating the brief on Jan. 30, 2026. Please refer to Microsoft’s website for the latest information. On Oct. 14, 2025, a critical, unauthenticated remote code execution (RCE) vulnerability was identified in Microsoft's Windows Server Update Services (WSUS), a core enterprise component for patch management. Microsoft's initial patch during the October Patch Tuesday did not fully address the flaw, necessitating an emergency out-of-band security update released Oct. 23, 2025. Within hours of the emergency update, Unit 42 and other security researchers observed active exploitation in the wild. The combination of a remotely exploitable, unauthenticated RCE in a core infrastructure service, coupled with observed active exploitation in the wild,…