A vulnerability has been identified in SIMATIC WinCC OA V3.16 (All versions in default configuration), SIMATIC WinCC OA V3.17 (All versions in non-default configuration), SIMATIC WinCC OA V3.18 (All versions in non-default configuration). Affected applications use client-side only authentication, when neither server-side authentication (SSA) nor Kerberos authentication is enabled. In this configuration, attackers could impersonate other users or exploit the client-server protocol without being authenticated.