CVE-2026-70492: CVE-2026-70492: Stored Cross-Site Scripting (XSS) via Unescaped KaTeX Render-Error Fallback in Open WebUI

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CVE-2026-70492: Stored Cross-Site Scripting (XSS) via Unescaped KaTeX Render-Error Fallback in Open WebUI

Vulnerability ID: CVE-2026-70492
CVSS Score: 8.7
Published: 2026-08-04

CVE-2026-70492 (also tracked as GHSA-pwxh-7358-jq2x) is a stored Cross-Site Scripting (XSS) vulnerability in Open WebUI versions 0.10.0 through 0.10.x. The flaw arises because engine-level JavaScript stack overflow errors escape KaTeX standard error handling. Svelte's fallback rendering path assigns the raw, unescaped mathematical input string directly to the DOM using the unsafe {@html} directive, enabling arbitrary client-side code execution. This allows attackers to steal session tokens and perform unauthorized administrative actions when users view malicious messages. The vulnerability has been fully resolved in version 0.11.0.

TL;DR

A stored XSS vulnerability in Open WebUI (v0.10.0 to <0.11.0) allows authenticated attackers to execute arbitrary JavaScript in user sessions by forcing a call stack limit error in KaTeX, bypassing error handling and triggering an unescaped HTML fallback rendering path.

⚠️ Exploit Status: POC

Technical Details

CWE ID: CWE-79
Attack Vector: Network (AV:N)
CVSS v3.1 Score: 8.7 (High)
Exploit Status: Proof-of-Concept Available
CISA KEV Status: Not Listed
Vulnerability Class: Stored Cross-Site Scripting (XSS)

Affected Systems

Open WebUI
open-webui: >= 0.10.0, < 0.11.0 (Fixed in: 0.11.0)

Code Analysis

Commit: bc600d3

Fix stored XSS vulnerability by escaping HTML entities in KatexRenderer fallback

@@ -38,7 +38,11 @@
        try {
            renderedHTML = renderToString(content, { displayMode, throwOnError: false });
        } catch {
-           renderedHTML = content;
+           renderedHTML = content
+               .replaceAll('&', '&amp;')
+               .replaceAll('<', '&lt;')
+               .replaceAll('>', '&gt;');
        }
    }

Mitigation Strategies

Upgrade Open WebUI to version 0.11.0 or higher.
Implement Web Application Firewall (WAF) rules to inspect and block inputs with excessively nested structures in mathematical blocks.
Manually escape HTML input in Svelte rendering fallback logic if immediate patching is unavailable.

Remediation Steps:

Check the current Open WebUI version through the administration panel or via the deployed container image tag.
Obtain the updated release package or container image corresponding to version 0.11.0 or higher.
Rebuild or redeploy the application service to apply the updated KatexRenderer component configurations.
Audit chat and channel database records for historical payloads containing nested braces paired with HTML event triggers.

References

Read the full report for CVE-2026-70492 on our website for more details including interactive diagrams and full exploit analysis.

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