vercel next.js up to 15.5.15/16.2.4 authentication bypass

Summaryinfo

A vulnerability was found in vercel next.js up to 15.5.15/16.2.4. It has been declared as critical. The impacted element is an unknown function. Such manipulation leads to authentication bypass. This vulnerability is documented as CVE-2026-44575. The attack can be executed remotely. There is not any exploit available. It is recommended to upgrade the affected component.

Detailsinfo

A vulnerability, which was classified as critical, has been found in vercel next.js up to 15.5.15/16.2.4. Affected by this issue is some unknown processing. The manipulation with an unknown input leads to a authentication bypass vulnerability. Using CWE to declare the problem leads to CWE-288. A product requires authentication, but the product has an alternate path or channel that does not require authentication. Impacted is confidentiality. CVE summarizes:

Next.js is a React framework for building full-stack web applications. From 15.2.0 to before 15.5.16 and 16.2.5, App Router applications that rely on middleware or proxy-based checks for authorization can allow unauthorized access through transport-specific route variants used for segment prefetching. In affected configurations, specially crafted .rsc and segment-prefetch URLs can resolve to the same page without being matched by the intended middleware rule, which can allow protected content to be reached without the expected authorization check. 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-2026-44575 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 314908 (Next.js Framework 15.2.x < 15.5.16 / 16.x < 16.2.5 Authorization Bypass), 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 (314908) 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/

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

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