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TI-2026-45207 Aliases CVE-2026-63428

Improper input validation in heyform

Priority HIGH 65CWE-20Published · Updated

Key facts

Attack vector
Network
Privileges required
None
User interaction
None
Attack complexity
Low
Impact type
Tampering
Confidentiality · integrity · availability
None · Low · None
Fix status
Fixed

Attack profile from CVSS 3.1 · CNA. Fix status from CNA. Impact type from CWE-915.

Summary

HeyForm is an open-source form builder. Prior to version 3.0.0-rc.9, `completeSubmission` accepts a `hiddenFields: [{id, name, value}]` array from the submitter and stores it verbatim in `submission.hiddenFields`, without validating the supplied `id`/`name` against the form's declared `form.hiddenFields` schema. An anonymous form submitter can therefore inject arbitrary key/value pairs (including XSS payloads, fake authorization metadata, integration-relevant values) into the stored submission. These fields are subsequently forwarded as-is to every webhook integration registered on the form. Version 3.0.0-rc.9 contains a patch for the issue.

Why it matters now

Exploitation Proof of concept CISA SSVC · not in CISA KEV
EPSS 0.00342 27th percentileScored 2026-11-07
Fix Fixed heyform (heyform): 3.0.0-rc.9

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
Poc
Automatable
Yes
Technical impact
Partial

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

VendorProductAffected versionsFixed inStatusSource
heyformheyformbefore 3.0.0-rc.93.0.0-rc.9Patch availableCNA
  • heyform Vendorheyform Affected before 3.0.0-rc.9 Fixed in 3.0.0-rc.9 Patch available CNA

Remediation

  • Fix · CNA heyform (heyform) Fixed in 3.0.0-rc.9

Timeline

  1. 2026-10-02 Threatist record created from CVE-2026-63428

References

Other 2

  • TI-2026-45208 HeyForm has unauthenticated /api/upload endpoint that accepts arbitrary files with no auth/session/form context CVSS 3.1HIGH 8.6
  • TI-2026-27351 HeyForm vulnerable to stored XSS via form field titles CVSS 3.1CRITICAL 9.0
  • TI-2026-56756 HeyForm Reflects Any Origin in CORS Responses While Allowing Credentials CVSS 3.1HIGH 8.1
  • TI-2026-33532 HeyForm Vulnerable to Stored XSS via Unauthenticated SVG File Upload CVSS 4.0MEDIUM 6.4
  • TI-2026-85482 Stored cross-site scripting in HeyForm via uploaded HTML files CVSS 3.1HIGH 7.6

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences