CVE-2026-44573
Next.js: Middleware / Proxy bypass in Pages Router applications using i18n
- Published
- May 13, 2026
- Updated
- Aug 13, 2026
- Assigning CNA
- GitHub_M
- Evidence observed
- Aug 25, 2026
Primary CVSS
nvd · CVSS 3.1
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:NLow · next 30 days
- Percentile
- 48.0%
- Model date
- Sep 21, 2026
EPSS is a statistical estimate, not a certainty or a measure of impact. Combine it with CVSS, KEV status, exposure and your environment.
Summary
Next.js is a React framework for building full-stack web applications. From 12.2.0 to before 15.5.16 and 16.2.5, Applications using the Pages Router with i18n configured and middleware/proxy-based authorization can allow unauthorized access to protected page data through locale-less /_next/data/<buildId>/<page>.json requests. In affected configurations, middleware does not run for the unprefixed data route, allowing an attacker to retrieve SSR JSON for protected pages without passing the intended authorization checks. This vulnerability is fixed in 15.5.16 and 16.2.5.
Sources
1Next.js v16.2.4 Security PoC Collection (CVE-2026-23870, CVE-2026-44575, CVE-2026-44579, CVE-2026-44574, CVE-2026-44578, CVE-2026-44573, CVE-2026-44581, CVE-2026-44580, CVE-2026-44577, CVE-2026-44576, CVE-2026-44582, CVE-2026-44572)
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