fix: /@fs/ dir traversal with escaped chars (fixes vitejs#8498)

packages/vite/src/node/server/middlewares/static.ts

@@ -123,7 +123,7 @@ export function serveRawFsMiddleware(
 
   // Keep the named function. The name is visible in debug logs via `DEBUG=connect:dispatcher ...`
   return function viteServeRawFsMiddleware(req, res, next) {
-    let url = decodeURI(req.url!)
+    let url = decodeURIComponent(req.url!)
     // In some cases (e.g. linked monorepos) files outside of root will
     // reference assets that are also out of served root. In such cases
     // the paths are rewritten to `/@fs/` prefixed paths and must be served by

playground/fs-serve/__tests__/fs-serve.spec.ts

@@ -52,6 +52,11 @@ describe.runIf(isServe)('main', () => {
     expect(await page.textContent('.unsafe-fs-fetch-status')).toBe('403')
   })
 
+  test('unsafe fs fetch with special characters (#8498)', async () => {
+    expect(await page.textContent('.unsafe-fs-fetch-8498')).toBe('')
+    expect(await page.textContent('.unsafe-fs-fetch-8498-status')).toBe('403')
+  })
+
   test('nested entry', async () => {
     expect(await page.textContent('.nested-entry')).toBe('foobar')
   })

playground/fs-serve/root/src/index.html

@@ -27,6 +27,8 @@ <h2>Safe /@fs/ Fetch</h2>
 <h2>Unsafe /@fs/ Fetch</h2>
 <pre class="unsafe-fs-fetch-status"></pre>
 <pre class="unsafe-fs-fetch"></pre>
+<pre class="unsafe-fs-fetch-8498-status"></pre>
+<pre class="unsafe-fs-fetch-8498"></pre>
 
 <h2>Nested Entry</h2>
 <pre class="nested-entry"></pre>
@@ -106,6 +108,16 @@ <h2>Denied</h2>
       console.error(e)
     })
 
+  // outside root with special characters #8498
+  fetch('/@fs/' + ROOT + '/root/src/%2e%2e%2f%2e%2e%2funsafe%2ejson')
+    .then((r) => {
+      text('.unsafe-fs-fetch-8498-status', r.status)
+      return r.json()
+    })
+    .then((data) => {
+      text('.unsafe-fs-fetch-8498', JSON.stringify(data))
+    })
+
   // not imported before, inside root with special characters, treated as safe
   fetch(
     '/@fs/' +