CVE-2026-114139: Sentry-Javascript: Middleware Bypass when using Tunnel route

The tunnelRoute option makes the SDK send browser events to a path on your own Next.js server (for example /monitoring), where a rewrite forwards them to Sentry to prevent ad blockers from blocking them. To keep those envelope requests from being rejected by your middleware, the SDK skips middleware for them.

The middleware skip was wider than the rewrite. The rewrite only serves requests to the tunnel path itself with the o and p parameters set. The skip applied to anything under the tunnel path. Requests in that gap go to your application instead of Sentry, and your middleware never runs on them.

Skipping middleware does not grant the request any privileges. Routes that check the session server-side are still protected.

You are affected only if all of the following are true:

1. tunnelRoute is set (a string path or true),
2. your app is built with webpack (Turbopack builds are not affected),
3. some route of your application resolves under the tunnel path. That could be a direct collision (/monitoring/foo with tunnelRoute: '/monitoring') or a dynamic segment at the route root (app/[locale]/…), which matches any first path segment, and
4. your middleware is the only place that enforces authorization for those routes.

Sentry’s own services, and the data in your Sentry organization, are not affected.