CVE-2026-64642: Next Middleware / Proxy Bypass Vulnerability

HIGH
Advisory Identifier: GHSA-6gpp-xcg3-4w24
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CWE-285
Published
Advisory Summary

CVE-2026-64642 is a HIGH middleware / proxy bypass vulnerability (CWE-285: Improper Authorization) affecting Next libraries in the npm ecosystem. The issue involves middleware / proxy bypass in app router applications using turbopack and single locale. Remediation is available by upgrading affected packages to version 16.2.11.

CVE-2026-64642 at a Glance

CVE Identifier CVE-2026-64642
GHSA Identifier GHSA-6gpp-xcg3-4w24
Severity HIGH
CVSS v3.1 Base Score N/A
CWE Classification CWE-285: Improper Authorization
Affected Product Next
Package Ecosystem npm
Published Date
Last Updated

How to Fix CVE-2026-64642

To remediate this vulnerability, upgrade all affected Next dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

next fixed: 16.2.11 
npm install next@16.2.11
Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

npm ls next

How to Check if You Are Affected

To determine whether your Node.js application is affected by CVE-2026-64642, inspect your project dependencies using npm:

npm ls next

Analyze the terminal output to locate any version of Next in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 16.2.11), your application is affected.

Note: The npm ls next command inspects dependencies declared in your package.json and lockfile; it does not perform automated runtime dynamic scanning.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-285: Improper Authorization, where the product does not perform or incorrectly performs an authorization check when an actor attempts to access a resource or perform an action. In Next, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

## Impact Crafted requests targeting Next.js applications using App Router built with Turbopack and a **single** entry in `config.i18n.locales` can bypass middleware/proxy based authentication. ## Workarounds If you cannot upgrade immediately, enforce authorization in the page's server-side data path instead of relying solely on middleware.

CVE-2026-64642 Affected Next Versions

1 component(s)
Fixed Versions:
16.2.11
Product / Package Ecosystem Affected Versions Fixed Version
next
npm/next
npm
≥ 16.0.0
< 16.2.11
16.2.11

References

GitHub Advisory / Wiki ADVISORY
https://github.com/vercel/next.js/security/advisories/GHSA-6gpp-xcg3-4w24
Next Source Repository REPOSITORY
https://github.com/vercel/next.js/pull/96014
Security Fix Commit FIX COMMIT
https://github.com/vercel/next.js/commit/6bf4df14508ad6c0cd46af50c6051ee42f2d9151
Next Source Repository REPOSITORY
https://github.com/vercel/next.js
Next Release RELEASE
https://github.com/vercel/next.js/releases/tag/v16.2.11

Frequently Asked Questions

What is CVE-2026-64642?
CVE-2026-64642 is a security vulnerability in Next involving Middleware / Proxy bypass in App Router applications using Turbopack and single locale under CWE-285: Improper Authorization.
Which Next versions are affected?
Affected versions include releases prior to 16.2.11 across affected packages: next.
What version fixes CVE-2026-64642?
Upgrading to 16.2.11 (or the latest patched release for your respective branch) resolves the vulnerability.
Is next affected?
Yes, next is affected in releases prior to 16.2.11. Upgrade your dependency to 16.2.11 or later.
What CWE is associated with CVE-2026-64642?
CVE-2026-64642 is classified under CWE-285: Improper Authorization (The product does not perform or incorrectly performs an authorization check when an actor attempts to access a resource or perform an action.).
How can I check npm dependencies for CVE-2026-64642?
Run the dependency tree command: 'npm ls next'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-6gpp-xcg3-4w24",
  "modified" : "2026-07-22T22:59:38Z",
  "published" : "2026-07-22T22:59:38Z",
  "aliases" : [ "CVE-2026-64642" ],
  "summary" : "Next.js: Middleware / Proxy bypass in App Router applications using Turbopack and single locale",
  "details" : "## Impact\n\nCrafted requests targeting Next.js applications using App Router built with Turbopack and a **single** entry in `config.i18n.locales` can bypass middleware/proxy based authentication.\n\n## Workarounds\n\nIf you cannot upgrade immediately, enforce authorization in the page's server-side data path instead of relying solely on middleware.",
  "severity" : [ {
    "type" : "CVSS_V4",
    "score" : "CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:L/VA:N/SC:N/SI:N/SA:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "npm",
      "name" : "next"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "16.0.0"
      }, {
        "fixed" : "16.2.11"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/vercel/next.js/security/advisories/GHSA-6gpp-xcg3-4w24"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/vercel/next.js/pull/96014"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/vercel/next.js/commit/6bf4df14508ad6c0cd46af50c6051ee42f2d9151"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/vercel/next.js"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/vercel/next.js/releases/tag/v16.2.11"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-285" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-07-22T22:59:38Z",
    "nvd_published_at" : null
  }
}