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CVE-2026-63428

5.8 · MEDIUM

HeyForm is an open-source form builder.

Published Jul 20, 2026CWE-20EPSS 0.34%

Overview

CVE-2026-63428 is a medium-severity vulnerability. It was published on July 20, 2026 and has a CVSS 3.1 base score of 5.8 (MEDIUM).

This vulnerability has a CVSS 3.1 base score of 5.8, rated MEDIUM. It can be exploited remotely over the network. No authentication or special privileges are required for exploitation.

Technical description

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.

Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

References

GitHubgithub.com/heyform/heyform/commit/092e255e9e02565de1b3c057f3dad849160952d2GitHubgithub.com/heyform/heyform/security/advisories/GHSA-r7vg-xh87-v4w3GitHubgithub.com/heyform/heyform/security/advisories/GHSA-r7vg-xh87-v4w3

How CyberStrike helps

Frequently asked questions

What is CVE-2026-63428?

CVE-2026-63428 is a medium-severity vulnerability. It was published on July 20, 2026 and has a CVSS 3.1 base score of 5.8 (MEDIUM).

How severe is CVE-2026-63428?

This vulnerability has a CVSS 3.1 base score of 5.8, rated MEDIUM. It can be exploited remotely over the network. No authentication or special privileges are required for exploitation.

How do I fix or remediate CVE-2026-63428?

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

How can CyberStrike help with CVE-2026-63428?

CyberStrike is an open-source, AI-augmented pentesting engine. Rather than flag a version number, it tests whether an issue like CVE-2026-63428 is actually reachable in your own applications and APIs, then verifies each finding before reporting it. That tells you if the weakness is a real, exploitable risk in your environment or a false positive you can safely deprioritize.

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