Missing Authorization in Open WebUI - #VU136843
Published: July 3, 2026
Vulnerability identifier: #VU136843
CSH Severity: Low
CVSS v4.0: CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:H/VA:L/SC:N/SI:N/SA:N/E:U/U:Clear
CVE-ID: N/A
CWE-ID: CWE-862
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vendor: Open WebUI
Affected software:
Open WebUI
Open WebUI
Detailed vulnerability description
The vulnerability allows a remote user to overwrite messages in channels they do not belong to.
The vulnerability exists due to improper access control in the chat completion API channel pipeline when handling chat completion requests with a channel:-prefixed chat_id and attacker-controlled message_id values. A remote user can send a specially crafted chat completion request to overwrite messages in channels they do not belong to.
The overwritten message retains the original author attribution while displaying attacker-controlled content, including in private and direct-message channels.
Remediation
Install security update from vendor's website.