That is not likely to help. All server logins automatically get a database user created for them in master and all users in master have execute permissions on sp_executesql. The issue is likely not the lack of permissions to execute sp_executesql itself, it's likely the lack of permissions of the user in the user-database that is executing the user-proc that calls sp_executesql to access the resources used by the dynamic sql submitted to sp_executesql.