PTC’s KEPServerEX Versions 6.0 to 6.14.263 are vulnerable to being made to read a recursively defined object that leads to uncontrolled resource consumption. KEPServerEX uses OPC UA, a protocol which defines various object types that can be nested to create complex arrays. It does not implement a check to see if such an object is recursively defined, so an attack could send a maliciously created message that the decoder would try to decode until the stack overflowed and the device crashed.