CVE-2026-54011 Open WebUI: Stored XSS in Mermaid Markdown Preview
Attackers can execute arbitrary JavaScript in victims' browsers via malicious Mermaid diagrams in Markdown previews, potentially leading to account takeover.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Over the internet
- Victim action needed
- A user has to click or open something
- Fix
- Available
What is CVE-2026-54011?
CVE-2026-54011 is a high-severity cross-site scripting vulnerability in Openwebui Open Webui, published on 23 Jun 2026. Any signed-in user can exploit it over the network, and only if a user opens a file or follows a link.
Official description
Open WebUI is a self-hosted artificial intelligence platform designed to operate entirely offline. Prior to 0.9.6,Open WebUI renders Mermaid blocks from Markdown files in the file preview panel and inserts the generated SVG into the DOM using innerHTML. Because Mermaid is configured with securityLevel: 'loose', attacker-controlled Mermaid content can be rendered unsafely in this flow. A working payload was validated through the Markdown preview path, resulting in JavaScript execution in the victim’s browser under the application origin. This vulnerability is fixed in 0.9.6.
Weakness: CWE-79
Which versions are affected by CVE-2026-54011?
3 open source packages ship an affected version, including open-webui. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
open-webui PyPI | All versions | 0.9.6 |
open-webui PyPI | All versions | 0.9.6 |
open-webui PyPI | All versions | 0.9.6 |
Products include Openwebui Open Webui.
How do I fix CVE-2026-54011?
Upgrade open-webui to 0.9.6 or later.
Escape output for the context it lands in and set a strict Content Security Policy. Upgrading the affected component is the real fix. More about Cross-site scripting.
Is CVE-2026-54011 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-54011 exists.
Other vulnerabilities in Openwebui Open Webui
- CVE-2026-44551 Open WebUI: LDAP Empty Password Authentication Bypass
- CVE-2026-56400 open-webui - Remote Code Execution via CORS Misconfiguration and Session Validation
- CVE-2024-8017 Cross-site Scripting (XSS) in open-webui/open-webui
- CVE-2026-45672 Open WebUI: Jupyter code execution works despite `ENABLE_CODE_EXECUTION=false` — feature gate bypassed
- CVE-2026-87995 Open WebUI: Same-origin XSS to account takeover via terminal port-preview iframe hardcoding allow-same-origin
Sources
Also known as GHSA-v8qj-hxv7-mgvv, PYSEC-2026-2759.