fix: ignore invalid accept-language header (vercel#26476)

Fixes vercel#22329

## Bug

- [x] Related issues linked using fixes vercel#22329
- [x] Integration tests added

## Feature

- [ ] Implements an existing feature request or RFC. Make sure the feature request has been accepted for implementation before opening a PR.
- [ ] Related issues linked using `fixes #number`
- [ ] Integration tests added
- [ ] Documentation added
- [ ] Telemetry added. In case of a feature if it's used or not.

## Documentation / Examples

- [ ] Make sure the linting passes

packages/next/build/webpack/loaders/next-serverless-loader/utils.ts

@@ -351,10 +351,15 @@ export function getUtils({
 
     let defaultLocale = i18n.defaultLocale
     let detectedLocale = detectLocaleCookie(req, i18n.locales)
-    let acceptPreferredLocale =
-      i18n.localeDetection !== false
-        ? accept.language(req.headers['accept-language'], i18n.locales)
-        : detectedLocale
+    let acceptPreferredLocale
+    try {
+      acceptPreferredLocale =
+        i18n.localeDetection !== false
+          ? accept.language(req.headers['accept-language'], i18n.locales)
+          : detectedLocale
+    } catch (_) {
+      acceptPreferredLocale = detectedLocale
+    }
 
     const { host } = req.headers || {}
     // remove port from host and remove port if present

packages/next/next-server/server/next-server.ts

@@ -427,11 +427,15 @@ export default class Server {
 
       let defaultLocale = i18n.defaultLocale
       let detectedLocale = detectLocaleCookie(req, i18n.locales)
-      let acceptPreferredLocale =
-        i18n.localeDetection !== false
-          ? accept.language(req.headers['accept-language'], i18n.locales)
-          : detectedLocale
-
+      let acceptPreferredLocale
+      try {
+        acceptPreferredLocale =
+          i18n.localeDetection !== false
+            ? accept.language(req.headers['accept-language'], i18n.locales)
+            : detectedLocale
+      } catch (_) {
+        acceptPreferredLocale = detectedLocale
+      }
       const { host } = req?.headers || {}
       // remove port from host if present
       const hostname = host?.split(':')[0].toLowerCase()

test/integration/i18n-support/test/index.test.js

@@ -267,6 +267,28 @@ describe('i18n Support', () => {
       expect($('#router-as-path').text()).toBe('/')
     })
 
+    it('should ignore the invalid accept-language header', async () => {
+      nextConfig.replace('localeDetection: false', 'localeDetection: true')
+      const res = await fetchViaHTTP(
+        ctx.appPort,
+        '/',
+        {},
+        {
+          headers: {
+            'accept-language': 'ldfir;',
+          },
+        }
+      )
+
+      expect(res.status).toBe(200)
+      const $ = cheerio.load(await res.text())
+      expect($('html').attr('lang')).toBe('en-US')
+      expect($('#router-locale').text()).toBe('en-US')
+      expect(JSON.parse($('#router-locales').text())).toEqual(locales)
+      expect($('#router-pathname').text()).toBe('/')
+      expect($('#router-as-path').text()).toBe('/')
+    })
+
     it('should set locale from detected path', async () => {
       for (const locale of nonDomainLocales) {
         const res = await fetchViaHTTP(