Results are presented on a search for a light charged Higgs boson that can be produced in the decay of the top quark t -> H(+)b and which, in turn, decays into tau(+)nu(tau). The analysed data correspond to an integrated luminosity of about 2 fb(-1) recorded in proton-proton collisions at root s = 7 TeV by the CMS experiment at the LHC. The search is sensitive to the decays of the top quark pairs t (t) over bar -> H(+/-)W(-/+)b (b) over bar and t (t) over bar -> H +/- H -/+ b (b) over bar. Various final states have been studied separately, all requiring presence of a tau lepton from H+ decays, missing transverse energy, and multiple jets. Upper limits on the branching fraction B(t -> H(+)b) in the range of 2-4% are established for charged Higgs boson masses between 80 and 160 GeV, under the assumption that B(H+ -> tau(+)nu(tau)) = 1.