fix: sort cookie chunks correctly (#8284)

packages/next-auth/src/core/lib/cookie.ts

@@ -161,9 +161,22 @@ export class SessionStore {
     }
   }
 
-  get value() {
-    return Object.values(this.#chunks)?.join("")
-  }
+ /**
+   * The JWT Session or database Session ID
+   * constructed from the cookie chunks.
+   */
+ get value() {
+  // Sort the chunks by their keys before joining
+  const sortedKeys = Object.keys(this.#chunks).sort((a, b) => {
+    const aSuffix = parseInt(a.split(".").pop() || "0")
+    const bSuffix = parseInt(b.split(".").pop() || "0")
+
+    return aSuffix - bSuffix
+  });
+
+  // Use the sorted keys to join the chunks in the correct order
+  return sortedKeys.map(key => this.#chunks[key]).join("")
+}
 
   /** Given a cookie, return a list of cookies, chunked to fit the allowed cookie size. */
   #chunk(cookie: Cookie): Cookie[] {