CVE-2026-54011: Open WebUI stored XSS in Mermaid Markdown preview

CVE-2026-54011 · Severity: high · CVSS 8.7 · Published 2026-06-23

Open WebUI is a self-hosted interface for interacting with artificial intelligence models. A security flaw allows an attacker to embed malicious code within Markdown files that, when viewed by another user, can execute commands in that user's browser. This could lead to unauthorized access to user data, session hijacking, or the performance of actions on behalf of the victim within the platform.

Technologies: open-webui (PyPI). Vendors: PyPI.

Quick answers

Is CVE-2026-54011 exploited in the wild?
No. Junglewise Threat Intelligence has no report of CVE-2026-54011 being exploited in the wild.
How severe is CVE-2026-54011?
High severity, with a CVSS score of 8.7, published 23 June 2026.
Which products and versions are affected?
open-webui (PyPI) <= 0.9.5, ECOSYSTEM:introduced=0,fixed=0.9.6.
Is there a fix for CVE-2026-54011?
Yes. open-webui (PyPI): upgrade to 0.9.6 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
How is CVE-2026-54011 attacked?
It is attacked over the network, in a network appliance.
Am I affected by CVE-2026-54011?
Check whether you run open-webui (PyPI) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

How to fix

  • open-webui (PyPI): upgrade to 0.9.6 or later
    pip install "open-webui>=0.9.6"

Technical details

A stored cross-site scripting (XSS) vulnerability exists in Open WebUI's file preview component. The application renders Mermaid diagram blocks from Markdown files and injects the resulting SVG directly into the DOM using 'innerHTML'. Because the Mermaid library is configured with 'securityLevel: loose', it does not sufficiently sanitize the output. An attacker with low privileges can upload a malicious .md file; when a victim previews this file, the attacker-controlled JavaScript executes under the application's origin. This issue is fixed in version 0.9.6 by transitioning to a stricter security configuration.

Affected products

  • Open WebUI Open WebUI < 0.9.6

Identifiers

  • CVE-2026-54011
  • GHSA-v8qj-hxv7-mgvv
  • PYSEC-2026-2759

Timeline

  • 2026-06-11: advisory: GitHub security advisory published
  • 2026-06-23: disclosed: NVD publication date

References

This page as Markdown. Free to reuse under CC BY 4.0 with a link back.