Computational hardness assumption from the syndrome decoding problem has been useful in designing the security of code based cryptosystem that are safe against quantum computing. Due to complexities in solution using high degree linearized polynomial equations modeled from subspaces, we proposed exploiting the dependency between subspaces in a Grassmann graph constructed from Boundary measurement maps by using copula functions. We also used copula functions to estimate the marginal distribution in these subspaces. Thereafter, the Maximum likelihood based estimation approach was used to search the codeword that maximizes the conditional distribution and in the process approximate a solution to the problem. Results of the Bit Error Rate performance obtained from simulation shows that the proposed solution performs better than the information set decoding method.