The title molecule, C14H11N3O4, is approximately planar, with an interplanar angle between the two benzene rings of 5.8 (2)°. In the crystal, four molecules are linked by an R44(12) motif with pairs of strong O—H...O and N—H...O hydrogen bonds. The motif is situated about the crystallographic centres of symmetry and it is composed of two pairs of parallel molecules. This quadruplet of molecules is further extended by symmetry-equivalent hydrogen bonds to form layers parallel to the (10overline{1}) plane. In addition to the hydrogen bonds, there is also a weak π–π interaction between the benzene rings.