Hi,
The picture says this can be the rising damp in your house. Rising damp is the problem in which the water rises up the wall causing the walls to become damp. The water gets evaporated and the salts present in the water affects the walls and the paint began to fall or sometimes, plaster may fall from the wall. It can result in the growth of moulds which affects the health and the property very badly. You need to treat this problem. You just have to search the source of water that is causing this problem and can treat that fault. If you are confused, you can hire a professional, as they will check the whole scenario and will give the best advice.