XSS in Open-Webui
CVE-2026-109300
Open WebUI from 0.6.31 before 0.11.4 contains a stored cross-site scripting vulnerability in its Markdown renderer, which treats user-authored tool-call details blocks as tool output and mounts their embeds attribute in script-enabled iframes. Authenticated users can post crafted channel messages, chat messages, or citation content that runs JavaScript in viewers' browsers, enabling in-app phishing, or session hijacking where iframeSandboxAllowSameOrigin is enabled.
Vulnerability class: XSS (Cross-Site Scripting)
Published .
CVSS v3 metric
CVSS v3 base score 4.6 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:L/I:L/A:N.
EPSS exploit prediction
No EPSS score from FIRST.org yet. New CVEs usually get one within a few days; no score means no signal yet, not low risk. How EPSS works.
Affected products
Weakness classification (CWE)
References
- github.com/open-webui/open-webui/security/advisories/GHSA-9wj4-mcm3-ppj6 (vendor-advisory)
- www.vulncheck.com/advisories/open-webui-0.6.31-before-0.11.4-stored-xss-via-too… (third-party-advisory)
Frequently asked questions
- What is CVE-2026-109300?
- CVE-2026-109300 is a medium-severity vulnerability in Open-Webui, classified under Cross-site Scripting. CVSS score: 4.6/10. Published 2026-10-12.
- How severe is CVE-2026-109300?
- Medium severity. CVSS v3 base score is 4.6 out of 10.