CVE-2026-70492

Open WebUI: Stored XSS via unescaped KaTeX render-error fallback in rendered messages

MEDIUM
5.4
CVSS Score
Published: August 4, 2026 at 08:53 PM UTC
Updated: September 18, 2026 at 02:59 PM UTC
1 product affected across 1 vendorOpen Webui

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Severity
MEDIUM5.4
Exploit prediction
EPSS 0.4%
SSVC
PoC

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.

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

v < 0.11.00.10.0 ≤ v < 0.11.0
Affected range stops below 0.11.0, so it looks safe — our inference, not a vendor statement

References (4)

x_refsource_CONFIRMExploitPatchVendor Advisory
Source: cverecord
https://github.com/open-webui/open-webui/security/advisories/GHSA-pwxh-7358-jq2x
x_refsource_MISCPatchVendor Advisory
Source: cverecord
https://github.com/open-webui/open-webui/pull/26718
x_refsource_MISCRelease Notes
Source: cverecord
https://github.com/open-webui/open-webui/releases/tag/v0.11.0

SSVC — Action Prioritization

SSVCPoCNot automatablePartial impact

SSVC signals action urgency (what to patch first), separate from CVSS which measures severity.

CVSS

Attack Vector
NETWORK
Complexity
LOW
Privileges
LOW
User Interaction
REQUIRED
Scope
CHANGED
Confidentiality
LOW
Integrity
LOW
Availability
NONE
Vector?

Quick Info

StatusANALYZED
CWE
CWE-79

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