CVE-2026-70492

Received Received - Intake

Stored XSS in Open WebUI via KaTeX Math Block

Publication date: 2026-08-04

Last updated on: 2026-08-04

Assigner: GitHub, Inc.

Description

Open WebUI is an extensible, feature-rich, and user-friendly self-hosted AI platform. From 0.10.0 until 0.11.0, src/lib/components/chat/Messages/Markdown/KatexRenderer.svelte could store and render a chat message whose math block makes KaTeX fail with a stack overflow instead of a parse error. The catch branch fell back to inserting the original math source into the page as HTML through {@html} rather than as text, so script in the message runs in the browser of whoever views it, including shared chats and channels. The viewer's session token in localStorage can be stolen, and an administrator viewer can have their account taken over. This issue is fixed in 0.11.0.

CVSS Scores

EPSS Scores

Probability:
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Meta Information

Published

2026-08-04

Last Modified

2026-08-04

Generated

2026-08-05

AI Q&A

2026-08-05

EPSS Evaluated

N/A

NVD

CVE-2026-70492

Affected Vendors & Products

Vendor	Product	Version / Range
open_webui	open_webui	From 0.10.0 (inc) to 0.11.0 (inc)

Helpful Resources

Exploitability

CWE

KEV

CWE ID	Description
CWE-79	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.

Attack-Flow Graph

Executive Summary

Open WebUI versions 0.10.0 to 0.11.0 had a flaw in the KaTeX math block renderer. When a chat message contained a malformed math block causing KaTeX to fail with a stack overflow, the error handling would insert the raw math source as HTML into the page using {@html}. This allowed malicious scripts in the message to execute in the browser of anyone viewing it, including shared chats or channels.

Detection Guidance

This vulnerability can be detected by checking the Open WebUI version in use. If your system runs versions between 0.10.0 and 0.11.0, it is vulnerable. Review chat messages containing math blocks for potential malicious scripts.

Impact Analysis

If you viewed a chat message with a specially crafted math block in vulnerable Open WebUI versions, an attacker could steal your session token from localStorage. An administrator viewing such a message could have their account compromised, leading to unauthorized access to the system.

Compliance Impact

This vulnerability could lead to unauthorized access to sensitive data, violating confidentiality requirements under GDPR and HIPAA. A successful exploit may result in data breaches, triggering mandatory breach notification and potential fines for non-compliance with these regulations.

Mitigation Strategies

Immediately upgrade Open WebUI to version 0.11.0 or later. Review and remove any suspicious chat messages containing math blocks. Monitor for unauthorized access or session token theft.

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