Prior to version 0.10.0, Open WebUI’s handling of channel thread parents did not bind the parent_id parameter to the channel expressed in the URL. An authenticated user could construct a request containing a parent_id that belonged to a different private or direct‑message channel, causing the server to return that channel’s thread context and message content. The flaw is a confidentiality failure classified as CWE‑639 and does not involve privilege escalation or system compromise.

All releases of open‑webui prior to v0.10.0 are affected. Administrators running open‑webui 0.9.x or earlier are vulnerable; the vulnerability was remedied in the v0.10.0 release, which enforces channel scoping for thread parents.

The CVSS score of 3.1 indicates low severity, and the EPSS score of < 1 % signifies a very low probability of exploitation in the wild. The vulnerability is not listed in the CISA KEV catalog. The attack vector is inferred to be an authenticated session, either local or remote, and the impact is confined to the disclosure of conversation content to users who have read permissions on private or DM channels; no further privileges are required.