Nuxt: Server-side route rules (`redirect`, `headers`, `proxy`, `ssr`) are skipped for case-variant paths when routing is case-insensitive

Impact

With the default router.options.sensitive: false, Nuxt's page router resolves routes case-insensitively, so /Admin renders the same page as /admin. On the server, however, route rules were resolved with Nitro's route-rule matcher, which matches keys case-sensitively. A request whose path differs from a rule key only in letter case therefore rendered the page with none of that rule applied.

Earlier fixes (GHSA-mm7m-92g8-7m47, GHSA-hxvh-4h3w-prp9) case-folded the route rules that the Nuxt app itself reads, such as appMiddleware. This advisory covers the rules applied on the server:

• redirect: a rule used to send visitors away from a page, such as '/admin/**': { redirect: '/login' }, was skipped, and the page and its server-fetched data were rendered instead.
• headers: per-route response headers, including security headers such as Content-Security-Policy or X-Frame-Options, were not sent.
• proxy: the request was not proxied.
• ssr: false and noScripts: the page was server-rendered, or shipped scripts, despite the rule.
• getRouteRules(event) (auto-imported, or from nuxt/server) and matchRouteRules from nuxt/server returned no rules for the case variant.

export default defineNuxtConfig({
  routeRules: {
    '/admin/**': { redirect: '/login' },
  },
})

With this configuration, /admin/secret redirects to /login, but /Admin/secret rendered app/pages/admin/secret.vue.

Mitigating factors

• Applications that set router.options.sensitive: true in nuxt.config are not affected, because their pages are only served for the exact case of the route.
• Access checks performed in server middleware, route middleware attached with definePageMeta, or in the page's data fetching are not affected. The issue only affects protections that rely on a server-side route rule matching the request path.

Affected versions

nuxt <4.6.2, including all Nuxt 3 releases, and @nuxt/nitro-server <4.6.2.

Patches

Fixed in [email protected]. Nuxt 3 reached end of life on 31 July 2026 and will not receive a fix.

Nuxt now resolves server-side route rules itself, decoding and case-folding both the rule keys and the request path unless router.options.sensitive is set, and applies the result to Nitro's redirect, headers and proxy handling, the renderer, and the getRouteRules / matchRouteRules helpers.

When routing is case-insensitive, patched releases change some behaviour:

• Route rules also apply to case variants of server API routes. For example, /API/x now matches a /api/** proxy or headers rule.
• Rule keys that differ only in letter case now resolve to the same path on the server, and the later key takes precedence.

The following are not changed by this fix:

• cache and swr response caching is attached to server routes by Nitro's router, which matches case-sensitively. A case variant is still rendered with its route rules applied, but its response is not cached.
• Rules that a deployment preset compiles into platform configuration (for example Vercel's config.json or Netlify's _redirects and _headers) are matched by the platform. Once a request reaches the Nuxt server, the rules are applied as described above.
• If sensitive is set only in app/router.options.ts, the server follows the nuxt.config value. In that configuration route rules can only apply to more paths, never fewer.

Workarounds

Upgrade to [email protected]. If you cannot upgrade, including on Nuxt 3:

1. Set router: { options: { sensitive: true } } in nuxt.config, so pages are only served for the exact case of their route.
2. Alternatively, enforce access control in server middleware or route middleware rather than relying on a redirect route rule, and set security headers for every response rather than per route.