CVE-2026-45797 heyform CVE debrief

Who should care

Users of HeyForm, especially those hosting it on their own servers, should be aware of this vulnerability and ensure they are running version 3.0.0-rc.7 or later to mitigate the risk. This includes operators, platform administrators, vulnerability management teams, and security teams who need to assess the impact of this vulnerability on their deployments.

Technical summary

The `/api/upload` endpoint in HeyForm allows unauthenticated file uploads, including SVG files. These SVG files are stored in the static assets directory and served with `Content-Type: image/svg+xml`. An attacker can exploit this by uploading a malicious SVG file that contains JavaScript code, which can then be executed by other users who access the file. This is a stored XSS vulnerability because the malicious code is stored on the server and executed when a user accesses the file. The vulnerability was patched in version 3.0.0-rc.7.

Defensive priority

Medium

Recommended defensive actions

• Update HeyForm to version 3.0.0-rc.7 or later
• Restrict access to the `/api/upload` endpoint to authenticated users only
• Validate and sanitize all uploaded files, especially SVG files
• Use a web application firewall (WAF) to detect and prevent XSS attacks
• Review compensating controls for exposed systems while remediation is scheduled and verified
• Check relevant monitoring, detection, and logs for exposed assets that need extra review
• Track exceptions, retest remediated assets, and close the item only after evidence is documented

Evidence notes

The CVE record was published on 2026-07-20T16:17:00.743Z and last modified on 2026-07-20T19:17:23.003Z. The NVD entry is currently in the 'Received' status. The vulnerability was patched in version 3.0.0-rc.7 of HeyForm. There are no known exploit details or reports of this vulnerability being used in attacks. However, defenders should verify that their deployments are updated to the patched version to prevent potential attacks.

Official resources