For the Central Licensing Server component used in ABB products ABB Ability™ System 800xA and related system extensions versions 5.1, 6.0 and 6.1, Compact HMI versions 5.1 and 6.0, Control Builder Safe 1.0, 1.1 and 2.0, Symphony Plus -S+ Operations 3.0 to 3.2 Symphony Plus -S+ Engineering 1.1 to 2.2, Composer Harmony 5.1, 6.0 and 6.1, Melody Composer 5.3, 6.1/6.2 and SPE for Melody 1.0SPx (Composer 6.3), Harmony OPC Server (HAOPC) Standalone 6.0, 6.1 and 7.0, ABB Ability™ System 800xA/ Advant® OCS Control Builder A 1.3 and 1.4, Advant® OCS AC100 OPC Server 5.1, 6.0 and 6.1, Composer CTK 6.1 and 6.2, AdvaBuild 3.7 SP1 and SP2, OPCServer for MOD 300 (non-800xA) 1.4, OPC Data Link 2.1 and 2.2, Knowledge Manager 8.0, 9.0 and 9.1, Manufacturing Operations Management 1812 and 1909, ABB AbilityTM SCADAvantage versions 5.1 to 5.6.5, a weakness in validation of input exists that allows an attacker to block license handling by sending specially crafted messages to the CLS web service.