While Kashmir has properly been on the U.N. agenda as part of the post-WWII decolonizing Trusteeship project, the status of Palestine, including Jerusalem, is governed by the post-WWI League of Nations Mandate of Palestine, which under Article 80 of the U.N. Charter the U.N. cannot modify without the permission of the recognized beneficiary: the Zionist Commission which eventually became the Israeli government. So while the U.N. has the legal right to mediate Kashmir matters it has none when it comes to Israel.