Summary
Open WebUI vulnerable to Stored XSS via iFrame embeds in response messages
Full technical description
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:
Edit the model response:
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.
On this object, add an embeds key and list value as shown below, forward the request and refresh the page.
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.
The same payload triggers when the chat is shared.
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.
Untrusted input is rendered as active markup in a victim's browser, which can run script in their session. Typical impact: session or credential theft, and actions taken as the user.
CVE-2026-26193 has a CVSS score of 7.3 (High). The vector is network-reachable, low privileges required, and user interaction required. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (0.6.44); upgrading removes the vulnerable code path.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
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Frequently Asked Questions
- What is CVE-2026-26193? CVE-2026-26193 is a high-severity cross-site scripting (XSS) vulnerability in open-webui (pip), affecting versions <= 0.6.43. It is fixed in 0.6.44. Untrusted input is rendered as active markup in a victim's browser, which can run script in their session.
- How severe is CVE-2026-26193? CVE-2026-26193 has a CVSS score of 7.3 (High). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
- Which versions of open-webui are affected by CVE-2026-26193? open-webui (pip) versions <= 0.6.43 is affected.
- Is there a fix for CVE-2026-26193? Yes. CVE-2026-26193 is fixed in 0.6.44. Upgrade to this version or later.
- Is CVE-2026-26193 exploitable, and should I be worried? Whether CVE-2026-26193 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether CVE-2026-26193 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix CVE-2026-26193? Upgrade
open-webuito 0.6.44 or later.