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.
CVE-2026-63428
MEDIUMPre-NVD 5.85.8—Trending — 3 sources updated this week
EchelonGraph scoreMEDIUM confidence
This medium-severity CVE scores 5.8 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit probability: 0.2%, top 84% of all CVEs by exploit prediction. GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).
Triggered by: NVD CVSS baseline
Sources: epss, secondary
5.8
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
- Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS: 0%CVSS: 5.8Exploit: NoneExposed: 0
No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.
- CVSS v3
- 5.8
- EG Score
- 5.8(medium)
- EG Risk
- 31(Track)EG Risk 31/100SSVC: Track
EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).
How it’s computedSeverity58% × 45%Exploitation0% × 40%Automatability30% × 15%Action: Routine — remediate on your standard cadence. - EPSS
- 16.4%
- KEV
- Not listed
Published
July 20, 2026
Last Modified
July 22, 2026
Advisory Details (2)
Auto-updated Jul 22, 2026🔬 Proof of concept available. Patch available. Sources: github_commit, github.
github Patch Available🟡 PoC Available
completeSubmission persists submitter-supplied hidden fields verbatim without validating against the form's declared hidden-field set · Advisory · heyform/heyform · GitHub
https://github.com/heyform/heyform/security/advisories/GHSA-r7vg-xh87-v4w3github_commit Patch Available
commit 092e255e9e02 (heyform/heyform)
Patch available: heyform/heyform v3.0.0-rc.9 (contains commit 092e255e9e02)
https://github.com/heyform/heyform/commit/092e255e9e02565de1b3c057f3dad849160952d2Weakness Classification(2)
MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.
Data Freshness Timeline
(refreshed 9× in last 7d / 9× in last 30d)
Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.
- 2026-07-23 03:22 UTCEG score recompute
- 2026-07-22 23:37 UTCEG score recompute
- 2026-07-22 14:08 UTCEPSS rescore
- 2026-07-22 14:08 UTCEPSS rescore
- 2026-07-21 15:25 UTCEPSS rescore
- 2026-07-21 15:25 UTCEPSS rescore
- 2026-07-20 16:37 UTCEG score recompute
- 2026-07-20 16:03 UTCEG score recompute
- 2026-07-20 16:02 UTCMITRE cvelistV5first tracked
Related CVEs(same CWE)
Frequently asked(5)
What is CVE-2026-63428?
CVE-2026-63428 is a medium vulnerability published on July 20, 2026. 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…
When was CVE-2026-63428 disclosed?
CVE-2026-63428 was first published in the National Vulnerability Database on July 20, 2026, with the most recent update on July 22, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-63428 actively exploited?
CVE-2026-63428 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 16.4% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.
What is the CVSS score of CVE-2026-63428?
CVE-2026-63428 has a CVSS v3 base score of 5.8 (NVD).
How do I remediate CVE-2026-63428?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-63428, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.
Dependency Blast Radius
Explore the affected products and dependency analysis for CVE-2026-63428
Is Your Infrastructure Affected by CVE-2026-63428?
EchelonGraph automatically scans your cloud infrastructure and maps CVE exposure using blast radius analysis.