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Next.js Middleware Authorization Bypass

ID: CVE-2025-29927-HEADLESS

Severity: critical

Author: ademking

Tags: cve,cve2025,headless,nextjs

Description

Section titled “Description”

A critical vulnerability in Next.js middleware allows attackers to bypass authorization checks by manipulating the x-middleware-subrequest header. This flaw affects Next.js versions prior to 14.2.25 and 15.2.3, potentially granting unauthorized access to sensitive resources.

YAML Source

Section titled “YAML Source”
id: CVE-2025-29927-HEADLESS


info:
  name: Next.js Middleware Authorization Bypass
  author: ademking
  severity: critical
  description: |
    A critical vulnerability in Next.js middleware allows attackers to bypass authorization checks by manipulating the x-middleware-subrequest header. This flaw affects Next.js versions prior to 14.2.25 and 15.2.3, potentially granting unauthorized access to sensitive resources.
  reference:
    - https://github.com/advisories/GHSA-f82v-jwr5-mffw
    - https://nvd.nist.gov/vuln/detail/CVE-2025-29927
    - https://www.tenable.com/cve/CVE-2025-29927
  classification:
    cvss-metrics: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
    cvss-score: 9.1
    cve-id: CVE-2025-29927
    cwe-id: CWE-285
  metadata:
    vendor: vercel
    product: Next.js
    framework: node.js
  tags: cve,cve2025,headless,nextjs


headless:
  - steps:
      - args:
          url: "{{BaseURL}}"
        action: navigate


      - action: waitstable


      - action: script
        name: nextjs_version
        args:
          code: |
            () => {
              if (!window.next || !window.next.version) {
                return "";
              }
              return window.next.version;
            }


    extractors:
      - type: dsl
        part: nextjs_version
        dsl:
          - '"Vulnerable Next.js => " + nextjs_version'


    matchers:
      - type: dsl
        dsl:
          - "compare_versions(nextjs_version, '>= 11.1.4', '<= 13.5.6')"
          - "compare_versions(nextjs_version, '> 14.0.0', '< 14.2.25')"
          - "compare_versions(nextjs_version, '> 15.0.0', '< 15.2.3')"
        condition: or
# digest: 4a0a00473045022100e7ef01315b5c9dff2e5567ad1421f5cf95ccaa62554a094e5faada3fe08261a10220611dab02751e9a58d17176f3632bd8a638191fc08abc6b7453a34abb9de3a5a0:922c64590222798bb761d5b6d8e72950

Guide to check the vulnerabilities

Section titled “Guide to check the vulnerabilities”

This template is used to detect vulnerabilities in web applications. It can be used with the Nuclei tool to scan for specific patterns or behaviors.

Terminal window
$ nuclei -u "URL" -t "headless/cves/2025/CVE-2025-29927-HEADLESS.yaml"

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