MD-11
Communication Breakdown
ATC Issue All Types; Deviation - Altitude Overshoot; Deviation / Discrepancy - Procedural Clearance
Air Traffic Control Issued Advisory / Alert; Air Traffic Control Issued New Clearance; Flight Crew Became Reoriented
Human Factors
During departure; both I and the pilot flying heard ATC clear us to FL140 and I read back FL140 to ATC. FL140 was set and confirmed in the FMS. Leveling at FL140; ATC stated our clearance was to FL120. They then cleared us to maintain FL140. Either both myself and the Pilot Flying heard FL140 instead of FL120 or ATC cleared us to FL140 when meaning to clear us to FL120. Whether actually cleared to FL140 or FL120 had ATC recognized our read back of a clearance to FL140 when they intended FL120 the situation could have been corrected.
MD11 Captain departing VHHH reports being cleared to FL140 by ATC. Upon leveling  at FL140; he is advised that the clearance was to FL120. Both pilots believe they heard and read back FL140.