Stored Cross-Site Scripting in Open WebUI Versions Prior to 0.11.4
CVE-2026-109300

5.1MEDIUM

Key Information:

Vendor

Open-webui

Status
Open-webui
Vendor
CVE Published:
12 October 2026

What is CVE-2026-109300?

Open WebUI versions prior to 0.11.4 are susceptible to a stored cross-site scripting (XSS) vulnerability in the Markdown renderer. This issue arises from the mishandling of user-authored tool-call detail blocks, which are improperly treated as tool output. Consequently, this vulnerability allows authenticated users to execute crafted channel messages, chat messages, or citation content that can run JavaScript in the browsers of users viewing the content. This raises serious security concerns including potential in-app phishing attacks and session hijacking, especially in scenarios where the iframeSandboxAllowSameOrigin attribute is enabled.

Affected Version(s)

open-webui 0.6.31 < 0.11.4

open-webui 0.11.4

References

https://github.com/open-webui/open-webui/security/advisor...
vendor-advisory
https://www.vulncheck.com/advisories/open-webui-0.6.31-be...
third-party-advisory

CVSS V4

Score:
5.1
Severity:
MEDIUM
Confidentiality:
Low
Integrity:
Low
Availability:
None
Attack Vector:
Network
Attack Complexity:
Low
Attack Required:
None
Privileges Required:
Undefined
User Interaction:
Unknown

Timeline

  • Vulnerability published

  • Vulnerability Reserved

Credit

KadirArslan
5yu4n
Classic298
.