GHSA-267c-6grr-h53f CVE-2026-44575

Next.js has a Middleware / Proxy bypass in App Router applications via segment-prefetch routes

High npm

Severity: 7.5 / 10; High · CVSS 3.1
Exploit chance (EPSS): 1.59%; Chance of exploitation in the next 30 days. Higher than 75.72% of scored vulnerabilities.
Known exploited: No; Not in CISA's catalog
Weakness: CWE-288 Authentication Bypass Using an Alternate Path or Channel
Fix: 15.5.16; Upgrade next to this version or later

Description

Impact

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.

Fix

We now include App Router transport variants when generating middleware matchers, so middleware protections are applied consistently to those requests as well as to the normal page URL.

Workarounds

If you cannot upgrade immediately, enforce authorization in the underlying route or page logic instead of relying solely on middleware.

Affected versions

npm

Package	Vulnerable	Fixed in
next	`>= 15.2.0, < 15.5.16`	`15.5.16`
next	`>= 16.0.0, < 16.2.5`	`16.2.5`

How to fix

Move to the fixed version or later with your package manager, update the lockfile, and run your tests. If the package only arrives through another dependency, upgrade that dependency first. If none of its releases pulls a fixed version yet, force the version with your package manager's override.

next npm → `15.5.16`

npm

npm install next@15.5.16

yarn

yarn add next@15.5.16

pnpm

pnpm add next@15.5.16

Severity breakdown

CVSS 3.1 7.5

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

Attack vector: Network
Attack complexity: Low
Privileges required: None
User interaction: None
Scope: Unchanged
Confidentiality: High
Integrity: None
Availability: None

Weakness

CWE-288: Authentication Bypass Using an Alternate Path or Channel

The product requires authentication, but the product has an alternate path or channel that does not require authentication.

How to prevent it

Architecture and Design: Funnel all access through a single choke point to simplify how users can access a resource. For every access, perform a check to determine if the user has permissions to access the resource.

References

Advisories

nvd.nist.gov/vuln/detail/CVE-2026-44575

Packages

github.com/vercel/next.js

Timeline

May 11, 2026 Published
Oct 26, 2026 Last updated by the source
Nov 1, 2026 Latest EPSS score

Advisory	Severity	Why it's related
GHSA-673q-mjm6-r5xr Next.js: Unauthenticated Remote Code Execution in `use cache` functions returning typed arrays	Critical	Also affects next
GHSA-2464-fhr4-w9xw Next.js: Unauthenticated Remote Code Execution in Image Optimization API when SVG files are used	Critical	Also affects next
GHSA-p3m5-59mp-jv5r Next.js: Denial of Service in App Router using Server Actions	High	Also affects next
GHSA-3w37-wq28-93x7 Next.js: Pending `use cache` fill can leak Draft Mode content into regular responses and persisted pages	Medium	Also affects next
GHSA-4jqv-mc3x-m676 Next.js has cache poisoning of SSG and ISR pages in self-hosted applications	Medium	Also affects next
GHSA-39w2-rjm5-chcv Next.js has information disclosure in development server's Model Context Protocol endpoint	Medium	Also affects next
GHSA-f87g-xv8r-7p7x Next.js has information disclosure in App Router metadata image routes via dynamicParams bypass	Medium	Also affects next
GHSA-mcj8-r9mp-w47p Next.js has cache poisoning in SSG/ISR rendering that leads to cross-user content substitution and persistent denial of service	Medium	Also affects next

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