Executive brief
Nuxt is a popular web framework used to build high-performance websites and applications. A security flaw was discovered where certain protection rules (such as login requirements) are ignored if a user accesses a web address using a mix of uppercase and lowercase letters. This could allow an unauthorized person to view private data or access restricted administrative pages simply by changing the capitalization of the URL.
Technical details
Nuxt matches route rules case-insensitively by default, but an incomplete fix for a previous vulnerability (CVE-2026-53721) resulted in an asymmetric matching process. While the lookup path is folded to lowercase, the route-rule keys compiled into the matcher remain verbatim (mixed-case). Consequently, rules defined with uppercase characters (e.g., /Admin) or derived from PascalCase page files fail to match. This allows attackers to bypass 'appMiddleware' auth gates and other route-level protections by requesting paths that vue-router serves case-insensitively but Nuxt fails to protect. The issue is resolved in versions 4.5.1 and 3.21.10 by ensuring both keys and lookups are normalized symmetrically.
Affected products
- Nuxt nuxt >= 4.4.7, < 4.5.1
- Nuxt nuxt >= 3.21.7, < 3.21.10
Timeline
- 2026-07-27: disclosed
- 2026-08-05: advisory
- 2026-08-05: patched