Here is a little code snippet to get the info about the users who have permission for a specific item in a list

Retrieving permissions for a Specific item -

private void GetItemPermission()
{
SecurableObject curObj = null;
ListItem curItem = ctx.Web.Lists.GetByTitle(“My List”).GetItemById(ItemId); -> Use ItemId of the Item.
//plug it into our query objectcurObj = curItem as SecurableObject;
IEnumerable roles = null;
roles = ctx.LoadQuery(
curObj.RoleAssignments.Include(
roleAsg => roleAsg.Member,
roleAsg => roleAsg.RoleDefinitionBindings.Include(
roleDef => roleDef.Name, // for each role def, include roleDef’s Name
roleDef => roleDef.Description)));
ctx.ExecuteQuery();
}