A vulnerability has been identified in SIMATIC HMI Comfort Panels 4" - 22" (All versions < V15.1 Update 1), SIMATIC HMI Comfort Outdoor Panels 7" & 15" (All versions < V15.1 Update 1), SIMATIC HMI KTP Mobile Panels KTP400F, KTP700, KTP700F, KTP900 und KTP900F (All versions < V15.1 Update 1), SIMATIC WinCC Runtime Advanced (All versions < V15.1 Update 1), SIMATIC WinCC Runtime Professional (All versions < V15.1 Update 1), SIMATIC WinCC (TIA Portal) (All versions < V15.1 Update 1), SIMATIC HMI Classic Devices (TP/MP/OP/MP Mobile Panel) (All versions). An attacker with network access to affected devices could potentially obtain a TLS session key. If the attacker is able to observe TLS traffic between a legitimate user and the device, then the attacker could decrypt the TLS traffic. The security vulnerability could be exploited by an attacker who has network access to the web interface of the device and who is able to observe TLS traffic between legitimate users and the web interface of the affected device. The vulnerability could impact the confidentiality of the communication between the affected device and a legitimate user. At the time of advisory publication no public exploitation of the security vulnerability was known.