The aircraft was on a scheduled passenger flight from Rome Ciampino (LIRA), Italy to Leipzig (EDDP), Germany. While climbing in Instrument Meteorological Conditions (IMC), it encountered sudden and unexpected severe turbulence in an area to the south of Perugia, Italy. At the time, the Cabin Crew were preparing for the in-flight service. One Cabin Crew Member (CCM) who was working in the rear galley was thrown into the air due to the severity of the event, struck the ceiling and fell heavily to the floor, sustaining a serious injury. The three other CCMs who were in the forward galley at the time were uninjured. All passengers were seated with their seat belts on and none were injured. No aircraft damage was reported. Probable Cause Unrestrained movement of the No. 2 CCM during sudden and unexpected severe turbulence. Contributory Factors Cb activity and turbulence was not forecast over peninsular Italy in the prognostic weather charts included in the Flight Crew?s briefing pack.