CVE-2026-45797CWE-434CWE-79

HeyForm Vulnerable to Stored XSS via Unauthenticated SVG File Upload

Medium · published July 20, 2026

CVSS v4.0
6.4
EPSS
1%
Percentile
46.4
In the wild
Unconfirmed
What it is

HeyForm is an open-source form builder. Prior to version 3.0.0-rc.7, the `/api/upload` endpoint allows unauthenticated file uploads including SVG files. Uploaded SVGs are stored in the static assets directory and served with `Content-Type: image/svg+xml` by Express's serve-static middleware, allowing an attacker to achieve stored cross-site scripting (XSS) on the heyform domain without any authentication. Version 3.0.0-rc.7 contains a patch for the issue.

The record
Technical detail
CVSS v4.0
6.4 · MEDIUM
Vector
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:N/VA:N/SC:H/SI:H/SA:N
EPSS
0.00570 · 46.4th percentile
Weaknesses
CWE-434 · Unrestricted Upload of File with Dangerous Type; CWE-79 · Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
Published
2026-07-20T15:43Z
EPSS history
Timeline
  • 20 JUL 15:43Z
    HeyForm Vulnerable to Stored XSS via Unauthenticated SVG File Upload
    cvelistv5