PT-2026-59388 · Pypi · Open-Webui

Published

2026-07-13

·

Updated

2026-07-13

CVSS v3.1

7.1

High

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

Description

There's an IDOR in the channels message management system that allows authenticated users to modify or delete any message within channels they have read access to. The vulnerability exists in the message update and delete endpoints, which implement channel-level authorization but completely lack message ownership validation.
While the frontend correctly implements ownership checks (showing edit/delete buttons only for message owners or admins), the backend APIs bypass these protections by only validating channel access permissions without verifying that the requesting user owns the target message. This creates a client-side security control bypass where attackers can directly call the APIs to modify other users' messages.
The vulnerability affects both message content modification and deletion, allowing users to tamper with message integrity and audit trails in collaborative channel environments.

Source - Sink Analysis

Source: User-controlled message id parameter in URL path
Call Chain:
  1. FastAPI route handlers update message by id() (line 450) and delete message by id() (line 630) in backend/open webui/routers/channels.py
  2. Channel-level authorization check: has access(user.id, type="read", access control=channel.access control) at lines 457 and 637
  3. Message retrieval: Messages.get message by id(message id) at lines 467 and 647
  4. Channel ID validation: if message.channel id != id: at lines 472 and 652
  5. Missing: Message ownership validation (message.user id == user.id)
  6. Sink: Messages.update message by id(message id, form data) at line 476 or Messages.delete message by id(message id) at line 658 - modifies any message without ownership verification

Proof of Concept

  1. Deploy Open WebUI with channels enabled (ENABLE CHANNELS=true)
  2. Create scenario:
  • User A creates a channel and grants User B read access
  • User A posts a message in the channel
  • User B observes the message id from the frontend
  1. Exploit: User B sends direct API requests bypassing frontend controls:
Message Update:
bash
curl -X POST "http://localhost:8080/api/v1/channels/{channel id}/messages/{victim message id}/update" 
   -H "Authorization: Bearer {attacker token}" 
   -H "Content-Type: application/json" 
   -d '{"content": "Malicious content injected by attacker"}'
Message Deletion:
bash
curl -X DELETE "http://localhost:8080/api/v1/channels/{channel id}/messages/{victim message id}/delete" 
   -H "Authorization: Bearer {attacker token}"
  1. Result: Victim's message is modified or deleted despite User B only having read permissions

Impact

  • Users can modify other users' message content within shared channels
  • Read-only users gain write/delete capabilities over other users' content

Remediation

Implement proper message ownership validation in the update and delete endpoints by adding ownership checks that follow the established security pattern used throughout the codebase. First, add a validation condition after the existing message retrieval to ensure only message owners or admins can modify messages: if user.role != "admin" and message.user id != user.id and not has access(user.id, type="write", access control=channel.access control) then raise a 403 Forbidden exception. Second, change the existing permission check from type="read" to type="write" for both update and delete operations to align with the access control model used in other routers (notes, prompts, knowledge, etc.).

Fix

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

Related Identifiers

PYSEC-2026-2746

Affected Products

Open-Webui