CVE-2026-44574: Next Next.js Has A Middleware / Vulnerability

HIGH
Advisory Identifier: GHSA-492v-c6pp-mqqv
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CVSS 8.1
CWE-288
Published
Advisory Summary

CVE-2026-44574 is a HIGH (CVSS 8.1) next.js has a middleware / vulnerability (CWE-288: Authentication Bypass Using an Alternate Path or Channel) affecting Next libraries in the npm ecosystem. The issue involves next.js has a middleware / proxy bypass through dynamic route parameter injection. Remediation is available by upgrading affected packages to version 15.5.16, 16.2.5.

CVE-2026-44574 at a Glance

CVE Identifier CVE-2026-44574
GHSA Identifier GHSA-492v-c6pp-mqqv
Severity HIGH
CVSS v3.1 Base Score 8.1
CWE Classification CWE-288: Authentication Bypass Using an Alternate Path or Channel
Affected Product Next
Package Ecosystem npm
Published Date
Last Updated

Security Impact

CVSS: 8.1

The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N).

Attack Vector Network (AV:N)
Attack Complexity Low (AC:L)
Privileges Required Low (PR:L)
User Interaction None (UI:N)
Scope Unchanged (S:U)
Confidentiality High (C:H)
Integrity High (I:H)
Availability None (A:N)

How to Fix CVE-2026-44574

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: 15.5.16 
npm install next@15.5.16
next fixed: 16.2.5 
npm install next@16.2.5
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-2026-44574, 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 15.5.16), 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-288: Authentication Bypass Using an Alternate Path or Channel, where the product requires authentication, but the product has an alternate path or channel that does not require authentication. 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 Applications that rely on middleware to protect dynamic routes can be vulnerable to authorization bypass. In affected deployments, specially crafted query parameters can alter the dynamic route value seen by the page while leaving the visible path unchanged, which can allow protected content to be rendered without passing the expected middleware check. ### Fix We now only honor internal route-parameter normalization in trusted routing flows and ignore externally supplied parameter encodings that should never have been accepted from ordinary requests. ### Workarounds If you cannot upgrade immediately, enforce authorization in route or page logic instead of relying solely on middleware path matching.

CVE-2026-44574 Affected Next Versions

2 component(s)
Fixed Versions:
15.5.1616.2.5
Product / Package Ecosystem Affected Versions Fixed Version
next
npm/next
npm
≥ 15.4.0
< 15.5.16
15.5.16
next
npm/next
npm
≥ 16.0.0
< 16.2.5
16.2.5

References

GitHub Advisory / Wiki ADVISORY
https://github.com/vercel/next.js/security/advisories/GHSA-492v-c6pp-mqqv
NVD — CVE-2026-44574 NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-44574
Next Source Repository REPOSITORY
https://github.com/vercel/next.js
Next Release RELEASE
https://github.com/vercel/next.js/releases/tag/v15.5.16
Next Release RELEASE
https://github.com/vercel/next.js/releases/tag/v16.2.5

Frequently Asked Questions

What is CVE-2026-44574?
CVE-2026-44574 is a security vulnerability in Next involving Next.js has a Middleware / Proxy bypass through dynamic route parameter injection under CWE-288: Authentication Bypass Using an Alternate Path or Channel.
Which Next versions are affected?
Affected versions include releases prior to 15.5.16, 16.2.5 across affected packages: next.
What version fixes CVE-2026-44574?
Upgrading to 15.5.16, 16.2.5 (or the latest patched release for your respective branch) resolves the vulnerability.
Is next affected?
Yes, next is affected in releases prior to 15.5.16, 16.2.5. Upgrade your dependency to 15.5.16, 16.2.5 or later.
What is the CVSS score of CVE-2026-44574?
CVE-2026-44574 has a CVSS v3.1 base score of 8.1 (HIGH) with vector string CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N.
What CWE is associated with CVE-2026-44574?
CVE-2026-44574 is classified under 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 can I check npm dependencies for CVE-2026-44574?
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-492v-c6pp-mqqv",
  "modified" : "2026-05-14T20:38:03Z",
  "published" : "2026-05-11T15:54:08Z",
  "aliases" : [ "CVE-2026-44574" ],
  "summary" : "Next.js has a Middleware / Proxy bypass through dynamic route parameter injection",
  "details" : "### Impact\n\nApplications that rely on middleware to protect dynamic routes can be vulnerable to authorization bypass. In affected deployments, specially crafted query parameters can alter the dynamic route value seen by the page while leaving the visible path unchanged, which can allow protected content to be rendered without passing the expected middleware check.\n\n### Fix\n\nWe now only honor internal route-parameter normalization in trusted routing flows and ignore externally supplied parameter encodings that should never have been accepted from ordinary requests.\n\n### Workarounds\n\nIf you cannot upgrade immediately, enforce authorization in route or page logic instead of relying solely on middleware path matching.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "npm",
      "name" : "next"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "15.4.0"
      }, {
        "fixed" : "15.5.16"
      } ]
    } ]
  }, {
    "package" : {
      "ecosystem" : "npm",
      "name" : "next"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "16.0.0"
      }, {
        "fixed" : "16.2.5"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/vercel/next.js/security/advisories/GHSA-492v-c6pp-mqqv"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-44574"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/vercel/next.js"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/vercel/next.js/releases/tag/v15.5.16"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/vercel/next.js/releases/tag/v16.2.5"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-288" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-05-11T15:54:08Z",
    "nvd_published_at" : "2026-05-13T17:16:22Z"
  }
}