CVE-2026-87994

Open WebUI: Channel members can overwrite another member's message via the chat completions endpoint

Open WebUI is an extensible, feature-rich, and user-friendly self-hosted AI platform. From 0.9.5 until 0.11.1, the channel branch of chat_completion in backend/open_webui/main.py checked channel write access and channel membership for a supplied message_id but did not verify that the calling user authored the targeted message. A channel member could use the chat completions endpoint to replace another member's message while preserving the victim as the stored author, altering the conversation record without gaining access to other channels. This issue is fixed in version 0.11.1.

Affected

open-webui

CVSS v3.1 GITHUB

4.3 MEDIUMCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N

EPSS

0.37% chance of exploitation in the next 30 days, 30th percentile

Published

2026-09-09

Updated

2026-09-10

Proof-of-concept exploits (1)

• advisories/GHSA-fmqh-xp37-5hr8

Security advisories

• open-webui/open-webui/security/advisories/GHSA-fmqh-xp37-5hr8
• open-webui/open-webui/pull/28631

References

• CVE Record
• NVD entry