CVE-2026-26193 — open-webui
HIGHCVE-2026-26193 is a high-severity (CVSS 7.3) Cross-site Scripting (XSS) vulnerability in open-webui. A fix is available for open-webui — see the affected versions and patch details below.
Open WebUI vulnerable to Stored XSS via iFrame embeds in response messages
Exploitation Status
No confirmed exploitation observed yet
- A successful exploit gives an attacker total control of the affected component, not partial access.
- CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.
Exploitation and automatability from CISA’s SSVC triage for CVE-2026-26193.
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
CVE-2026-26193 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.
Where this sits among everything scored
Of 382,621 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.
Real-World Exposure
open-webuiReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects PyPI packages — download data is not available via public APIs for these ecosystems.
Description
Summary
Manually modifying chat history allows setting the embeds property on a response message, the content of which is loaded into an iFrame with a sandbox that has allow-scripts and allow-same-origin set, ignoring the "iframe Sandbox Allow Same Origin" configuration. This enables stored XSS on the affected chat. This also triggers when the chat is in the shared format. The result is a shareable link containing the payload that can be distributed to any other users on the instance.
Details
The flaw stems from how iFrames are constructed here: https://github.com/open-webui/open-webui/blob/6f1486ffd0cb288d0e21f41845361924e0d742b3/src/lib/components/chat/Messages/ResponseMessage.svelte#L689-L703
messages.embeds is a user controlled property and so can be arbitrarily set by the user to a payload of their choosing. Since allowScripts and allowSameOrigin are harcoded as true here the sandboxing offers essentially no protection.
PoC
Create an arbitrary chat:
<img width="2468" height="1426" alt="image" src="https://github.com/user-attachments/assets/41e32f5c-3fa7-4208-a71f-85556eec6309" />
Edit the model response:
<img width="632" height="192" alt="image" src="https://github.com/user-attachments/assets/b1e79303-360f-46e3-8d6d-3309c3ec30af" />
<img width="2150" height="434" alt="image" src="https://github.com/user-attachments/assets/78f19d7f-10dc-4e91-83cc-2d4811e58496" />
Before saving, configure the browser to use an HTTP proxy tool (Burp/Caido/ZAP) and intercept the save request. Find the object within the history and then messages objects (not the messages array) that corresponds to the edited text.
<img width="2024" height="1528" alt="image" src="https://github.com/user-attachments/assets/953e5368-8e93-428b-b223-c695eacfe7b9" />
On this object, add an embeds key and list value as shown below, forward the request and refresh the page.
<img width="1904" height="1530" alt="image" src="https://github.com/user-attachments/assets/0e56be6f-5513-490e-9961-972bdfbd5d8b" />
This results in XSS via the controlled content getting rendered in the iFrame. Note the bold text is just to aid demonstration. console.log is used to prove JS execution because the lack of allow-modals on the iFrame sandbox prevents alerts.
<img width="2752" height="1686" alt="image" src="https://github.com/user-attachments/assets/4858f7b3-4e2f-4fab-a5a5-196df26bcdce" />
The same payload triggers when the chat is shared.
<img width="2730" height="1426" alt="image" src="https://github.com/user-attachments/assets/ee88b538-9781-4276-b681-9953974b826d" />
Impact
Any user can create a weaponised chat that can be shared and subsequently used to target other users.
Low privilege users are at risk of having their session taken over by a payload that reads their token from local storage and exfiltrates it to an attacker controlled server.
Admins are at risk of exposing the server to RCE via same chain described in GHSA-w7xj-8fx7-wfch.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐍PyPI | open-webui | all versions | 0.6.44pip install --upgrade 'open-webui==0.6.44' |
Affected Products
open webuiopenwebuiDetection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for open-webui, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update open-webui to 0.6.44 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-26193 is resolved across your whole dependency graph.
Workarounds
Escape or sanitise the affected output on the server side rather than relying on client-side filtering, and add a Content-Security-Policy that blocks inline script execution so injected markup cannot run even if it reaches the page.
Frequently Asked Questions
Is CVE-2026-26193 in your dependencies?
Find it across PyPI, including transitive dependencies.