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Stored XSS via SVG file upload on the /view endpoint

High
mattmillerai published GHSA-rj8c-c4p8-3c5h Jul 15, 2026

Package

pip ComfyUI (pip)

Affected versions

< 0.28.0

Patched versions

0.28.0

Description

Summary

The /view endpoint served uploaded SVG files inline because image/svg+xml was missing from its dangerous-Content-Type blocklist, allowing stored XSS.

Details

/view's blocklist forced application/octet-stream for HTML/JS/CSS but omitted image/svg+xml, and it did not set Content-Disposition: attachment. An attacker uploads (unauthenticated by default, e.g. via /upload/image) a malicious SVG carrying inline <script>; opening /view?filename=evil.svg&type=input renders it inline and executes the script same-origin, bypassing the cross-site origin checks.

Impact

Same-origin script can exfiltrate the JavaScript-accessible Comfy API token, read browser-stored workflows and settings, and issue authenticated-equivalent API calls.

Patches

Fixed in ComfyUI v0.28.0: image/svg+xml and the wider XML dialect family are routed through is_dangerous_content_type to a forced download (application/octet-stream + attachment + nosniff).

Workarounds

Do not open untrusted /view SVG URLs; restrict access to the ComfyUI instance.

Severity

High

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v3 base metrics

Attack vector
Network
Attack complexity
Low
Privileges required
None
User interaction
Required
Scope
Changed
Confidentiality
High
Integrity
Low
Availability
None

CVSS v3 base metrics

Attack vector: More severe the more the remote (logically and physically) an attacker can be in order to exploit the vulnerability.
Attack complexity: More severe for the least complex attacks.
Privileges required: More severe if no privileges are required.
User interaction: More severe when no user interaction is required.
Scope: More severe when a scope change occurs, e.g. one vulnerable component impacts resources in components beyond its security scope.
Confidentiality: More severe when loss of data confidentiality is highest, measuring the level of data access available to an unauthorized user.
Integrity: More severe when loss of data integrity is the highest, measuring the consequence of data modification possible by an unauthorized user.
Availability: More severe when the loss of impacted component availability is highest.
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:L/A:N

CVE ID

CVE-2026-56670

Weaknesses

Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')

The product does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users. Learn more on MITRE.

Credits