Neb. Rev. Stat. §§ 43-116
When any court in the State of Nebraska shall (1) have entered of record a decree of adoption prior to August 27, 1949, it shall be conclusively presumed that such adoption and all instruments and proceedings in connection therewith are valid in all respects notwithstanding some defect or defects may appear on the face of the record, or the absence of any record of such court, unless an action shall be brought within two years from August 27, 1949, attacking its validity, or (2) hereafter enter of record such a decree of adoption, it shall in like manner be conclusively presumed that the adoption and all instruments and proceedings in connection therewith are valid in all respects notwithstanding some defect or defects may appear on the face of the record, or the absence of any record of such court, unless an action is brought within two years from the entry of such decree of adoption attacking its validity.
Neb. Rev. Stat. §§ 43-116