PT-2026-59355 · Pypi · Open-Webui

Published

2026-07-13

·

Updated

2026-07-13

CVSS v3.1

5.4

Medium

VectorAV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N

Channel Access Grants Bypass filter allowed access grants

Affected Component

Channel creation and update endpoints:
  • backend/open webui/routers/channels.py (lines 291-340, create new channel)
  • backend/open webui/routers/channels.py (lines 617-638, update channel by id)
  • backend/open webui/models/channels.py (lines 825-826, set access grants call without filtering)

Affected Versions

Current main branch (commit 6fdd19bf1) and likely all versions supporting user-created group channels with access grants.

Description

All resource routers in Open WebUI (knowledge, models, notes, prompts, tools, skills) call filter allowed access grants() before persisting access grants. This function strips principal id: "*" wildcard grants from users who lack the relevant sharing.public * permission, and strips individual user grants from users who lack access grants.allow users permission.
The channel router does not call filter allowed access grants on either create or update paths. A non-admin user who can create group channels (or who owns a channel) can submit arbitrary access grants — including public wildcard grants — and those grants are stored verbatim, bypassing the admin's permission framework.
python
# channels.py — access grants from form data flow directly into persistence
# No call to filter allowed access grants() anywhere in these paths.

# Compare with knowledge.py / models.py / notes.py / prompts.py / tools.py / skills.py,
# all of which do:
#   form data.access grants = filter allowed access grants(user, form data.access grants)
# before creating or updating.

Attack Scenario

  1. Admin configures permissions so that regular users do NOT have sharing.public channels — public sharing of channels is intended to be admin-only.
  2. Attacker (a regular user) creates or owns a group channel.
  3. Attacker sends:
POST /api/v1/channels/
{
 "name": "public-channel",
 "type": "group",
 "access control": {
  "access grants": [
   {"principal type": "user", "principal id": "*", "permission": "read"}
  ]
 }
}
  1. set access grants is called directly without filter allowed access grants — the wildcard grant is persisted.
  2. The channel becomes publicly readable to every user on the instance, despite the admin's policy prohibiting public channels for regular users.
The same attack works via POST /api/v1/channels/{id}/update for any channel the attacker owns.

Impact

  • Regular users can bypass the sharing.public channels permission and make channels publicly accessible
  • Regular users can bypass access grants.allow users to grant individual-user access in environments where only group-based sharing is intended
  • Admin's permission framework for channels is silently ineffective
  • Creates an inconsistency with every other resource type in the codebase, making the security posture harder to reason about

Preconditions

  • Attacker must have an account with the ability to create group channels (default user capability), or ownership of an existing channel
  • Admin must have configured restrictive sharing permissions for regular users (otherwise there's no policy to bypass)

Fix

Found an issue in the description? Have something to add? Feel free to write us 👾
dbugs@ptsecurity.com

Related Identifiers

PYSEC-2026-2711

Affected Products

Open-Webui