Improper Authorization in Next.js - CVE-2026-64642
Published: July 22, 2026
Vulnerability identifier: #VU139032
CSH Severity: High
CVSS v4.0: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:L/VA:N/SC:N/SI:N/SA:N/E:U/U:Amber
CVE-ID: CVE-2026-64642
CWE-ID: CWE-285
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vendor: vercel
Affected software:
Next.js
Next.js
Detailed vulnerability description
The vulnerability allows a remote attacker to bypass middleware or proxy-based authentication and gain unauthorized access to protected application content.
The vulnerability exists due to improper authorization in App Router applications when processing crafted requests in builds using Turbopack with a single entry in config.i18n.locales. A remote attacker can send a specially crafted request to bypass middleware or proxy-based authentication and gain unauthorized access to protected application content.
Only App Router applications built with Turbopack and configured with a single locale are vulnerable.
How to mitigate CVE-2026-64642
Install security update from vendor's website.