VULNpocalypse

CVE-2026-63429: HeyForm has unauthenticated /api/upload endpoint that accepts arbitrary files with no auth/session/form context

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 2026-11-04 15:41 UTC. Rebuilt every few hours from cve-scores, CISA KEV and vedas-signatures. How this works and its limits.

What it is

HeyForm is an open-source form builder. Prior to version 3.0.0-rc.9, `POST /api/upload` has no authentication guard, no global guard, no form-context validation, no `openToken` requirement, and no session cookie check. Any anonymous internet user can upload files (PDF, DOC/DOCX, XLS/XLSX, CSV, TXT, MP4, images, etc., up to 10 MB) and receive a permanent public URL on the HeyForm domain. The endpoint is used by both authenticated form creators and unauthenticated form submitters; because no form-context binding exists, every request to it is anonymously accepted. Version 3.0.0-rc.9 contains a patch for the issue.

Description quoted from the CVE record (assigned by GitHub_M, published 2026-07-20).

Weakness: CWE-306: Missing Authentication for Critical Function; CWE-434: Unrestricted Upload of File with Dangerous Type

How it can be exploited

Exploitable over the network with low attack complexity needing no privileges and no user interaction. Impact: confidentiality low, integrity high, availability low. CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:H/A:L

CISA assessment (SSVC): CISA assesses that a public proof of concept exists. Automatable: yes. Technical impact: partial.

Public exploit evidence (Exploit Observer)

Exploit Observer found 2 code repositories naming this CVE.

Code repositories that name a CVE are often scanners, copies or fakes, and some are malware. Read the code before running anything.

See all 4 references on Exploit Observer

Live scores

EPSS
0.005
low predicted chance of attack
VEDAS
0.985
strong exploit evidence
On CISA KEV
Not listed
Detection rule
Nuclei

Who is affected

ProductAffectedNot affected
heyformversion < 3.0.0-rc.9Not stated

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

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)

HeyForm - Unauthenticated Arbitrary File Upload

HeyForm prior to 3.0.0-rc.9 exposes POST /api/upload with no authentication guard, no form-context validation and no session check. The handler (upload.controller.ts, @Post(‘/upload’) with a global ‘api’ prefix) accepts a multipart ‘file’ field from any anonymous client and returns a permanent public URL along with the original filename and size. This template uploads a uniquely-named benign file and confirms the endpoint accepts it unauthenticated by matching the returned filename, size and url fields.

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

The template sends 1 request (POST /api/upload); it decides using status, word matchers. Severity in the template: high. 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-2026-63429.yaml
Show the template (55 lines)
yaml
id: CVE-2026-63429

info:
  name: "HeyForm - Unauthenticated Arbitrary File Upload"
  author: vedas-arpsyndicate
  severity: high
  description: |
    HeyForm prior to 3.0.0-rc.9 exposes POST /api/upload with no authentication guard, no form-context
    validation and no session check. The handler (upload.controller.ts, @Post('/upload') with a global
    'api' prefix) accepts a multipart 'file' field from any anonymous client and returns a permanent public
    URL along with the original filename and size. This template uploads a uniquely-named benign file and
    confirms the endpoint accepts it unauthenticated by matching the returned filename, size and url fields.
  reference:
    - https://www.exploit.observer/?keyword=CVE-2026-63429&match=exact
    - https://subdomain.center/?engine=ammonites&keyword=heyform&match=exact
  classification:
    cvss-metrics: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:H/A:L
    cvss-score: 8.6
    cve-id: CVE-2026-63429
    cwe-id: CWE-434
  metadata:
    verified: false
  tags: cve,cve2026,heyform,upload,intrusive

variables:
  boundary: "{{rand_text_alphanumeric(18)}}"
  marker: "vedas{{rand_text_alphanumeric(10)}}"

http:
  - raw:
      - |
        POST /api/upload HTTP/1.1
        Host: {{Hostname}}
        Content-Type: multipart/form-data; boundary={{boundary}}

        --{{boundary}}
        Content-Disposition: form-data; name="file"; filename="{{marker}}.txt"
        Content-Type: text/plain

        {{marker}}
        --{{boundary}}--

    matchers-condition: and
    matchers:
      - type: status
        status:
          - 200
          - 201
      - type: word
        part: body
        words:
          - '"url"'
          - '"filename"'
          - '{{marker}}'
        condition: and

CVE-2026-63429.yaml on GitHub

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.

Supporting partners

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