Deactivated Channel Members Retain Full Access to Group/DM Channels

Affected Component

Channel membership authorization check:

• backend/open_webui/models/channels.py (lines 663-673, is_user_channel_member)
• Used at 15 locations in backend/open_webui/routers/channels.py

Affected Versions

Current main branch (commit 6fdd19bf1) and likely all versions with the group/DM channel feature.

Description

The is_user_channel_member function checks whether a ChannelMember row exists but does not check the is_active field. When a user is deactivated from a group or DM channel (removed by the channel owner, or leaves voluntarily), their membership row persists with is_active=False and status='left'. Because the authorization check ignores this field, the deactivated user retains full read and write access to the channel via direct API calls.

The channel correctly disappears from the deactivated user's channel list (the listing query at get_channels_by_user_id properly filters on is_active), but all 15 message-level endpoints in the router rely on is_user_channel_member for authorization, which does not filter on is_active.

# models/channels.py:663 — missing is_active check
def is_user_channel_member(self, channel_id, user_id, db=None):
    membership = db.query(ChannelMember).filter(
        ChannelMember.channel_id == channel_id,
        ChannelMember.user_id == user_id,
    ).first()
    return membership is not None  # True even when is_active=False

Compare with get_channel_by_id_and_user_id (line 778) which correctly checks ChannelMember.is_active.is_(True).

CVSS 3.1 Breakdown