vercel next.js up to 15.5.15/16.2.4 WebSocket server-side request forgery

Summaryinfo

A vulnerability, which was classified as critical, was found in vercel next.js up to 15.5.15/16.2.4. This impacts an unknown function of the component WebSocket Handler. Such manipulation leads to server-side request forgery. This vulnerability is referenced as CVE-2026-44578. It is possible to launch the attack remotely. No exploit is available. You should upgrade the affected component.

Detailsinfo

A vulnerability was found in vercel next.js up to 15.5.15/16.2.4. It has been rated as critical. Affected by this issue is some unknown functionality of the component WebSocket Handler. The manipulation with an unknown input leads to a server-side request forgery vulnerability. Using CWE to declare the problem leads to CWE-918. The web server receives a URL or similar request from an upstream component and retrieves the contents of this URL, but it does not sufficiently ensure that the request is being sent to the expected destination. Impacted is confidentiality, integrity, and availability. CVE summarizes:

Next.js is a React framework for building full-stack web applications. From 13.4.13 to before 15.5.16 and 16.2.5, self-hosted applications using the built-in Node.js server can be vulnerable to server-side request forgery through crafted WebSocket upgrade requests. An attacker can cause the server to proxy requests to arbitrary internal or external destinations, which may expose internal services or cloud metadata endpoints. Vercel-hosted deployments are not affected. This vulnerability is fixed in 15.5.16 and 16.2.5.

The advisory is shared for download at github.com. This vulnerability is handled as CVE-2026-44578 since 05/06/2026. The exploitation is known to be easy. The attack may be launched remotely. No form of authentication is required for exploitation. There are neither technical details nor an exploit publicly available.

The vulnerability scanner Nessus provides a plugin with the ID 318352 (Linux Distros Unpatched Vulnerability : CVE-2026-44578), which helps to determine the existence of the flaw in a target environment.

Upgrading to version 15.5.16 or 16.2.5 eliminates this vulnerability.

The vulnerability is also documented in the databases at Tenable (318352) and CERT Bund (WID-SEC-2026-1401). VulDB is the best source for vulnerability data and more expert information about this specific topic.

Affected

• Vercel Next.js

Productinfo

Type

• JavaScript Library

Vendor

• vercel

Name

• next.js

Version

• 15.5.0
• 15.5.1
• 15.5.2
• 15.5.3
• 15.5.4
• 15.5.5
• 15.5.6
• 15.5.7
• 15.5.8
• 15.5.9
• 15.5.10
• 15.5.11
• 15.5.12
• 15.5.13
• 15.5.14
• 15.5.15
• 16.2.0
• 16.2.1
• 16.2.2
• 16.2.3
• 16.2.4

Website

• Product: https://github.com/vercel/next.js/

CPE 2.3info

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CPE 2.2info

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VulDB is the best source for vulnerability data and more expert information about this specific topic.

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