VULNpocalypse

CVE-2026-21858: n8n Vulnerable to Unauthenticated File Access via Improper Webhook Request Handling

Advisory generated from the CVE record, CISA, Exploit Observer and VEDAS: what it is, whether it is exploited, who is affected, and how to fix and detect it.

Generated by VEDAS. Scores as of 2026-11-01 19:19 UTC. Rebuilt every few hours from cve-scores, CISA KEV and vedas-signatures. How this works and its limits.

What it is

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.

Description quoted from the CVE record (assigned by GitHub_M, published 2026-01-07).

Weakness: CWE-20: Improper Input Validation

How it can be exploited

Exploitable over the network with low attack complexity needing no privileges and no user interaction. Impact: confidentiality high, integrity high, availability none. CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:N

CISA assessment (SSVC): CISA has no evidence of exploitation. Automatable: yes. Technical impact: total.

Public exploit evidence (Exploit Observer)

Also known as: BDU:2026-00126, CNNVD-202601-1364, EUVD-2026-1187, GHSA-v4pr-fm98-w9pg

VEDAS cluster: VEDAS:BARKBREAKER

Exploit Observer links 28 pieces of public exploit code or detection modules that name this CVE or one of its aliases.

Exploit code and modules (28)

Code that names this CVE. A repository can be a working exploit, a scanner, a fake or malware; read it before running anything.

Research and write-ups (8)

Vulnerability databases and vendor advisories (6)

Catalogue entries, not exploit evidence.

171 more references returned by Exploit Observer did not name this CVE or an alias, so they are left out.

VEDAS data as of 2026-11-01T17:12 UTC; fetched 2026-11-02.

Live scores

EPSS
0.782
very likely to be attacked soon
VEDAS
0.988
strong exploit evidence
On CISA KEV
Not listed
Detection rule
Nuclei · Suricata

Who is affected

ProductAffectedNot affected
n8n-io n8nversion >= 1.65.0, < 1.121.0Not stated

Version ranges exactly as the CVE record states them. “Before X” means X is the first fixed version.

Exploit Observer also maps it to: n8n n8n, npm n8n, сообщество_свободного_программного_обеспечения n8n.

How to fix it

No fixed version or vendor advisory is listed in the CVE record yet. Watch the vendor’s security page.

How to detect it

Nuclei template (active check)

N8n - Improper Input Validation

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.

Name and description quoted from the template, written by VEDAS.

The template sends 2 requests (GET /signin, GET /rest/sentry.js); it decides using dsl, regex, status, word matchers. Severity in the template: critical. Marked as not yet verified against a live vulnerable target.

Run it against a host you own or are authorised to test:

bash
nuclei -u https://your-host -t CVE-2026-21858.yaml
Show the template (95 lines)
yaml
id: CVE-2026-21858

info:
  name: "N8n - Improper Input Validation"
  author: vedas-arpsyndicate
  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.
  reference:
    - https://www.exploit.observer/?keyword=CVE-2026-21858&match=exact
    - https://subdomain.center/?engine=ammonites&keyword=n8n&match=exact
  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
    cwe-id: CWE-20
  metadata:
    verified: false
  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')

CVE-2026-21858.yaml on GitHub

Suricata rules (network detection)

1 rule that alert on traffic matching this exploit: VEDAS CVE-2026-21858 N8n - Improper Input Validation. Add them to your Suricata rule set and reload.

Show the rules
suricata
alert http $EXTERNAL_NET any -> $HTTP_SERVERS $HTTP_PORTS (msg:"VEDAS CVE-2026-21858 N8n - Improper Input Validation"; flow:established,to_server; http.uri; content:"/rest/sentry.js"; nocase; fast_pattern; classtype:web-application-attack; reference:cve,CVE-2026-21858; reference:url,https://www.exploit.observer/?keyword=CVE-2026-21858&match=exact; reference:url,https://subdomain.center/?engine=ammonites&keyword=n8n&match=exact; sid:1010297; rev:1;)

CVE-2026-21858.rules on GitHub

Advisories on this CVE

References

Other references

Other databases

Where this comes from

This advisory is generated automatically by VEDAS from: CVE.org record, cve-scores (EPSS and VEDAS), Exploit Observer, vedas-signatures. Text in quotes is reproduced from the source; everything else is a fixed template filled with source fields. Nothing here is written by a language model. Check the vendor advisory before acting, and read how VEDAS and Exploit Observer work, and their limits.