Improper access control in Next.js - CVE-2026-44578
Published: May 6, 2026
Vulnerability identifier: #VU130279
CSH Severity: High
CVSS v4: 8.7 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N]
CVE-ID: CVE-2026-44578
CWE-ID: CWE-284
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vulnerability details
The vulnerability allows a remote attacker to disclose sensitive information.
The vulnerability exists due to improper access control in WebSocket upgrade handling in the built-in Node.js server when processing crafted WebSocket upgrade requests. A remote attacker can send a specially crafted WebSocket upgrade request to disclose sensitive information.
Only self-hosted applications using the built-in Node.js server are affected; Vercel-hosted deployments are not affected.
Affected software
Next.js
How to mitigate CVE-2026-44578
Install security update from vendor's website.
Next.js - addressed in versions 15.5.16, 16.2.5