We examine the level-crossing resonance in a cesium vapor cell filled with a buffer gas under counterpropagating pump and probe light waves with orthogonal linear polarizations. An optical transition Fg=4→Fe=3 is excited in the D1 line. Probe-wave transmission is analyzed versus a static magnetic field applied along the wave vectors. This configuration can provide ultrahigh-contrast electromagnetically induced absorption resonances. We report here a new, to the best of our knowledge, magneto-optical effect in the resonance shift caused by a transverse magnetic field and discuss how it can be applied in vector magnetometry.