Summary
Next.js: Middleware / Proxy bypass in App Router applications using Turbopack and single locale
Advisory details
Impact
Crafted requests targeting Next.js applications using App Router built with Turbopack and a single entry in config.i18n.locales can bypass middleware/proxy based authentication.
Workarounds
If you cannot upgrade immediately, enforce authorization in the page's server-side data path instead of relying solely on middleware.
References
- https://github.com/advisories/GHSA-6gpp-xcg3-4w24
- https://github.com/vercel/next.js/security/advisories/GHSA-6gpp-xcg3-4w24
- https://github.com/vercel/next.js/pull/96014
- https://github.com/vercel/next.js/commit/6bf4df14508ad6c0cd46af50c6051ee42f2d9151
- https://github.com/vercel/next.js/releases/tag/v16.2.11
Related vulnerabilities
All Supply chain →- HIGHCVE-2026-55212
Pimcore: Insufficient Permission Check on Class Definition Creation Endpoint Allows Privilege Escalation
- MEDIUMCVE-2026-55547
Yamcs's Missing Authorization on Role and Privilege Enumeration Endpoints Allows Any Authenticated User to Disclose Full Security Configuration
- HIGHCVE-2026-55065
Vikunja vulnerable to Improper Authorization and Authorization Bypass Through User-Controlled Key
- MEDIUMCVE-2026-54766
Vikunja has a project duplication bypasses write-permission check on the target parent project
- HIGHCVE-2026-55571
djust authentication bypass: a login_required / on_mount LiveView mount redirect does not close the WebSocket, allowing an unauthenticated client to dispatch event-handler calls
- MEDIUMCVE-2026-54624
django CMS: Structure endpoint bypasses page-view permission