CVE-2026-56672: CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') in Comfy-Org ComfyUI
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.
AI Analysis
Technical Summary
ComfyUI, a node-based diffusion model GUI and backend, had a stored XSS vulnerability (CWE-79) in versions before 0.28.0. The GET /userdata/{file} endpoint served user-controlled HTML and SVG files with MIME types based on file extensions, allowing embedded scripts to execute with same-origin privileges. This permitted attackers to steal sensitive browser-stored API tokens and settings, and perform API calls with the victim's privileges. The POST /userdata endpoint allowed storing arbitrary request bodies in the user's userdata directory, which could then be served unsafely. The /view endpoint had protections forcing dangerous MIME types to download, but these were not applied to /userdata. The vulnerability is resolved in ComfyUI version 0.28.0.
Potential Impact
Successful exploitation allows an attacker to execute stored cross-site scripting attacks within the ComfyUI origin. This can lead to theft of browser-stored API tokens, user settings, workflows, and enable authenticated-equivalent API calls, compromising user data and control over the application. The vulnerability does not affect availability but impacts confidentiality and integrity.
Mitigation Recommendations
This vulnerability is fixed in ComfyUI version 0.28.0. Users should upgrade to version 0.28.0 or later to remediate this issue. No other official remediation or temporary fixes are documented. Patch status is confirmed by the vendor advisory stating the fix is included in version 0.28.0.
CVE-2026-56672: CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') in Comfy-Org ComfyUI
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.
CVSS v3.1
Score 8.2high
Affected software
Comfy-Org
ComfyUI
Weaknesses
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
ComfyUI, a node-based diffusion model GUI and backend, had a stored XSS vulnerability (CWE-79) in versions before 0.28.0. The GET /userdata/{file} endpoint served user-controlled HTML and SVG files with MIME types based on file extensions, allowing embedded scripts to execute with same-origin privileges. This permitted attackers to steal sensitive browser-stored API tokens and settings, and perform API calls with the victim's privileges. The POST /userdata endpoint allowed storing arbitrary request bodies in the user's userdata directory, which could then be served unsafely. The /view endpoint had protections forcing dangerous MIME types to download, but these were not applied to /userdata. The vulnerability is resolved in ComfyUI version 0.28.0.
Potential Impact
Successful exploitation allows an attacker to execute stored cross-site scripting attacks within the ComfyUI origin. This can lead to theft of browser-stored API tokens, user settings, workflows, and enable authenticated-equivalent API calls, compromising user data and control over the application. The vulnerability does not affect availability but impacts confidentiality and integrity.
Mitigation Recommendations
This vulnerability is fixed in ComfyUI version 0.28.0. Users should upgrade to version 0.28.0 or later to remediate this issue. No other official remediation or temporary fixes are documented. Patch status is confirmed by the vendor advisory stating the fix is included in version 0.28.0.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- GitHub_M
- Date Reserved
- 2026-06-22T16:39:01.043Z
- Cvss Version
- 3.1
- State
- PUBLISHED
Threat ID: 6a6c31249c2644c7f8578d67
Added to database: 07/31/2026, 05:22:44 UTC
Last enriched: 07/31/2026, 13:03:35 UTC
Last updated: 09/14/2026, 22:01:35 UTC
Views: 53
Community Reviews
0 reviewsCrowdsource mitigation strategies, share intel context, and vote on the most helpful responses. Sign in to add your voice and help keep defenders ahead.
Want to contribute mitigation steps or threat intel context? Sign in or create an account to join the community discussion.
Actions
Updates to AI analysis require Pro Console access. Upgrade inside Console → Billing.
Need more coverage?
Upgrade to Pro Console for AI refresh and higher limits.
For incident response and remediation, OffSeq services can help resolve threats faster.
Latest Threats
Check if your credentials are on the dark web
Instant breach scanning across billions of leaked records. Free tier available.