n8n Webhooks - Remote Code Execution

criticalseverity

10CVSS score

78.2%likelihood of exploitation, next 30 days

100%of all CVEs are less likely

Readycheck to confirm it

n8n is an open source workflow automation platform. Versions starting with 1.65.0 and below 1.121.0 enable an attacker to access files on the underlying server through execution of certain form-based workflows. A vulnerable workflow could grant access to an unauthenticated remote attacker, resulting in exposure of sensitive information stored on the system and may enable further compromise depending on deployment configuration and workflow usage. This issue is fixed in version 1.121.0.

Impact

Unauthenticated remote attackers can access sensitive files, potentially leading to information disclosure and further system compromise.

Fix

Update to version 1.121.0 or later.

How to confirm it

Send: GET {{BaseURL}}/signin
Positive when: contains "<title>n8n.io" AND status 200 AND compare_versions(version, ">= 1.65.0", "< 1.121.0")
Send: GET {{BaseURL}}/rest/sentry.js
Positive when: contains "\"release\"" AND status 200 AND compare_versions(version, '>= 1.65.0', '< 1.121.0')

Run it with nuclei: nuclei -id CVE-2026-21858 -u <target>

The full check

id: CVE-2026-21858

info:
  name: n8n Webhooks - Remote Code Execution
  author: rxerium
  severity: critical
  description: |
    n8n is an open source workflow automation platform. Versions starting with 1.65.0 and below 1.121.0 enable an attacker to access files on the underlying server through execution of certain form-based workflows. A vulnerable workflow could grant access to an unauthenticated remote attacker, resulting in exposure of sensitive information stored on the system and may enable further compromise depending on deployment configuration and workflow usage. This issue is fixed in version 1.121.0.
  impact: |
    Unauthenticated remote attackers can access sensitive files, potentially leading to information disclosure and further system compromise.
  remediation: |
    Update to version 1.121.0 or later.
  reference:
    - https://thehackernews.com/2026/01/critical-n8n-vulnerability-cvss-100.html
    - https://nvd.nist.gov/vuln/detail/CVE-2026-21858
  classification:
    cvss-metrics: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:N
    cvss-score: 10.0
    cve-id: CVE-2026-21858
    epss-score: 0.78188
    epss-percentile: 0.9958
    cwe-id: CWE-20
  metadata:
    verified: true
    max-request: 2
    shodan-query: http.favicon.hash:-831756631
  tags: cve,cve2026,n8n,workflow,rce,vkev,vuln

flow: http(1) || http(2)

http:
  - method: GET
    path:
      - "{{BaseURL}}/signin"

    host-redirects: true
    max-redirects: 3

    extractors:
      - type: regex
        name: base64_content
        group: 1
        regex:
          - '<meta name="n8n:config:sentry" content="([A-Za-z0-9+/=]+)"'
        internal: true

      - type: dsl
        name: version
        dsl:
          - 'replace_regex(base64_decode(base64_content), ".*n8n@([0-9]+\\.[0-9]+\\.[0-9]+).*", "$1")'
        internal: true

      - type: dsl
        dsl:
          - '"n8n Version: " + version'

    matchers-condition: and
    matchers:
      - type: word
        part: body
        words:
          - "<title>n8n.io"
        case-insensitive: true

      - type: status
        status:
          - 200

      - type: dsl
        dsl:
          - 'compare_versions(version, ">= 1.65.0", "< 1.121.0")'

  - method: GET
    path:
      - "{{BaseURL}}/rest/sentry.js"

    extractors:
      - type: regex
        name: version
        group: 1
        regex:
          - 'release":"([0-9.]+)"'
        internal: true

      - type: dsl
        dsl:
          - '"n8n Version: " + version'

    matchers-condition: and
    matchers:
      - type: word
        part: body
        words:
          - '"release"'
        case-insensitive: true

      - type: status
        status:
          - 200

      - type: dsl
        dsl:
          - compare_versions(version, '>= 1.65.0', '< 1.121.0')

References

Use this check only on systems you are authorised to test. Where the data comes from