🔴 Critical | Source: Microsoft Security Response Center
CVE-2026-56165 is a heap-based buffer overflow vulnerability in Microsoft Account that allows an unauthenticated attacker to remotely execute arbitrary code over a network without requiring any user interaction. This is particularly serious because Microsoft Account underpins authentication across a vast range of Azure and Microsoft 365 services. Successful exploitation could allow an attacker to take control of affected systems or pivot deeper into connected cloud environments.
Security Architect’s Take: Ensure all Microsoft Account-related endpoints and services are patched immediately, and review network-level controls to restrict unnecessary exposure of Microsoft Account services to untrusted networks — prioritise this given the unauthenticated, network-exploitable attack vector.
Original advisory: CVE-2026-56165 Microsoft Account Remote Code Execution Vulnerability