All certificates of redemption of property issued by the State Land Office under Acts 1934, No. 161; Acts 1935, Fourth Ex. Sess., No. 14; Acts 1936, No. 183; Acts 1938, No. 47, and the cancellation of taxes made by authority thereof, are ratified, validated and confirmed unless attacked within six months from July 31, 1940.
La. R.S. § 41:1326