CVE-2026-44559

Missing Access Check on Channel Members Endpoint for Standard Channels

Affected Component

Channel members listing endpoint:

• backend/open_webui/routers/channels.py (lines 445-507, get_channel_members_by_id)

Affected Versions

Current main branch and likely all versions with the channels feature.

Description

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.

# Line 467-469: only group/dm channels are checked
if channel.type in ['group', 'dm']:
    if not Channels.is_user_channel_member(channel.id, user.id, db=db):
        raise HTTPException(...)
# Standard channels fall through with NO access check

Compare with other channel endpoints (e.g., get_channel_messages at line 688) which correctly call channel_has_access(user.id, channel, permission='read') for standard channels.

CVSS 3.1 Breakdown

Attack Scenario

1. Attacker obtains a private standard channel's UUID (via logs, browser history, URL observation, or other API responses).
2. Attacker calls GET /api/v1/channels/{id}/members.
3. The server returns the full list of permitted users including their IDs, names, emails, roles, and profile images.
4. The attacker has no access to the channel's messages (those endpoints check access correctly), but now knows exactly who does.

Preconditions

• Channels feature must be enabled (disabled by default)
• Attacker must know the channel UUID (not guessable, but obtainable through indirect means)

• Leaks the identity and personal details of every user with access to a private channel
• Reveals organizational structure and project assignments
• Enables targeted social engineering against channel members

The application does not perform an authorization check before performing a sensitive operation. Typical impact: unauthorized access to restricted functionality or data.

CVE-2026-44559 has a CVSS score of 4.3 (Medium). The vector is network-reachable, low privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (0.9.0); upgrading removes the vulnerable code path.

Kodem intelligence

1. What is CVE-2026-44559? CVE-2026-44559 is a medium-severity missing authorization vulnerability in open-webui (pip), affecting versions <= 0.8.12. It is fixed in 0.9.0. The application does not perform an authorization check before performing a sensitive operation.
2. How severe is CVE-2026-44559? CVE-2026-44559 has a CVSS score of 4.3 (Medium). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which versions of open-webui are affected by CVE-2026-44559? open-webui (pip) versions <= 0.8.12 is affected.
4. Is there a fix for CVE-2026-44559? Yes. CVE-2026-44559 is fixed in 0.9.0. Upgrade to this version or later.
5. Is CVE-2026-44559 exploitable, and should I be worried? Whether CVE-2026-44559 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
6. What actually determines whether CVE-2026-44559 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
7. How do I fix CVE-2026-44559? Upgrade open-webui to 0.9.0 or later.