CVE-2026-44574: Next.js: Middleware / Proxy bypass through dynamic route parameter injection

Severity: high (CVSS 8.1 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.6% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-05-13 · updated 2026-10-26
Weakness: CWE-288

Description

Next.js is a React framework for building full-stack web applications. From 15.4.0 to before 15.5.16 and 16.2.5, applications that rely on middleware to protect dynamic routes can be vulnerable to authorization bypass. In affected deployments, specially crafted query parameters can alter the dynamic route value seen by the page while leaving the visible path unchanged, which can allow protected content to be rendered without passing the expected middleware check. This vulnerability is fixed in 15.5.16 and 16.2.5.

Affected products

Next.js: from 15.4.0 before 15.5.16; from 16.0.0 before 16.2.5 — fixed in 15.5.16, 16.2.5

How to fix

Upgrade to a fixed version: Next.js 15.5.16, 16.2.5. Check the vendor advisory for mitigations.

References

Get alerted when CVE-2026-44574 or the next vulnerability affects your stack