What’s Vulnerable › Vulnerabilities

CVE-2026-87994: Open WebUI: Channel members can overwrite another member's message via the chat completions endpoint

• Severity: medium (CVSS 4.3 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.4% probability of exploitation in the next 30 days
• Public exploit or detection template: yes
• Published: 2026-09-09 · updated 2026-09-16
• Weakness: CWE-639

Description

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 products

• open-webui: from 0.9.5 before 0.11.1 — fixed in 0.11.1

How to fix

Upgrade to a fixed version: open-webui 0.11.1. Check the vendor advisory for mitigations.

References

• https://github.com/open-webui/open-webui/commit/7d392bedc9c1aaecc94509a58e59186b614433dc
• https://github.com/open-webui/open-webui/pull/28631
• https://github.com/open-webui/open-webui/releases/tag/v0.11.1
• https://github.com/open-webui/open-webui/security/advisories/GHSA-fmqh-xp37-5hr8
• https://github.com/open-webui/open-webui/security/advisories/GHSA-fmqh-xp37-5hr8

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