CVE-2026-44559: Open WebUI: Missing Access Check on Channel Members Endpoint for Standard Channels

Severity: medium (CVSS 4.3 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.2% probability of exploitation in the next 30 days
Public exploit or detection template: yes
Published: 2026-05-15 · updated 2026-06-17
Weakness: CWE-862

Description

Open WebUI is a self-hosted artificial intelligence platform designed to operate entirely offline. Prior to 0.9.0, the GET /api/v1/channels/{id}/members endpoint only checks membership for group and dm channel types (lines 467-469). For standard channels — including private ones — there is no channel_has_access check before returning the member list. Any authenticated user who knows a private channel's UUID can enumerate all users with access to that channel. This vulnerability is fixed in 0.9.0.

Affected products

open-webui: before 0.9.0 — fixed in 0.9.0

How to fix

Upgrade to a fixed version: open-webui 0.9.0. Check the vendor advisory for mitigations.

References

Get alerted when CVE-2026-44559 or the next vulnerability affects your stack