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CVE-2026-59215 is an improper access control vulnerability affecting Open WebUI, a self‑hosted AI platform that enables users to create and manage conversations within channels, including private and direct message (DM) environments. The flaw exists in versions prior to 0.10.0 and stems from a failure to properly enforce channel boundaries when handling thread parent and reply operations.
In Open WebUI, each channel (public, private, or DM) has a unique identifier. Messages within a channel are organised as threads, with each message carrying a `parent_id` that links it to a specific thread. The vulnerable endpoint processes requests that reference a `parent_id` but does not validate that this `parent_id` belongs to the channel being accessed. Concretely, when a user navigates to a thread URL, the application does not bind the `parent_id` to the channel context from the URL. This allows an authenticated attacker to manually craft a URL containing a `parent_id` from a private or DM channel they do not belong to, and the application will render the thread context without performing any authorisation checks.
The core technical issue is the lack of a binding between the `parent_id` parameter and the channel identifier in the backend query. The application accepts a `parent_id` value and retrieves the corresponding message thread, but it never verifies that the channel associated with that `parent_id` matches the channel the user is currently viewing. Because the user is already authenticated, the system trusts the request and serves the content, effectively bypassing the channel‑based isolation model. This is a classic case of CWE‑639 (Authorization Bypass Through User‑Controlled Key), where an attacker can manipulate a resource identifier to gain unauthorised access.
The attack vector is network‑based, requires low privileges (authenticated user), and involves high attack complexity due to the need to guess or enumerate valid `parent_id` values. However, once a valid ID is obtained (e.g., through information leakage or brute‑force), the attacker can silently read private conversations, including sensitive data shared in restricted channels. The vulnerability undermines the trust model of collaborative environments, as users expect their private channels to remain inaccessible to others.
The fix in version 0.10.0 implements proper channel context binding: every request that references a `parent_id` now enforces that the referenced message belongs to the currently accessed channel, rejecting any cross‑channel reference. This closes the gap by adding a server‑side authorisation check that compares the channel ID from the URL with the channel ID of the parent message.
DailyCVE Form:
Platform: Open WebUI
Version: <0.10.0
Vulnerability: Authorization Bypass
Severity: LOW (CVSS 3.1)
date: 2026-07-09
Prediction: 2026-07-09
What Undercode Say:
Analytics – detecting potential exploitation can be performed by monitoring URL patterns and API requests that contain `parent_id` parameters. The following `bash` commands and code snippets can help identify anomalous cross‑channel references:
Monitor access logs for unusual parent_id parameters
grep "parent_id=" /var/log/openwebui/access.log | awk -F 'parent_id=' '{print $2}' | cut -d'&' -f1 | sort | uniq -c | sort -nr
Curl request to test for the vulnerability (replace CHANNEL_ID and PARENT_ID)
curl -X GET "https://openwebui.example.com/channel/CHANNEL_ID/thread?parent_id=PARENT_ID" \
-H "Authorization: Bearer <valid_token>"
Python snippet to brute‑force parent_id values (for authorised testing only)
import requests
for pid in range(1000, 2000):
r = requests.get(f"https://openwebui.example.com/channel/1/thread?parent_id={pid}",
headers={"Authorization": "Bearer <token>"})
if r.status_code == 200 and "private" in r.text:
print(f"Potential leak: {pid}")
Exploit:
An authenticated attacker can exploit this vulnerability by:
- Identifying a valid `parent_id` from a private or DM channel (e.g., through social engineering, information disclosure, or by enumerating sequential IDs).
- Constructing a URL that points to a public or accessible channel but appends the stolen `parent_id` as a query parameter.
- Sending the request to the server; the application will retrieve and display the thread context associated with that `parent_id` without verifying channel membership.
- Repeating the process for multiple `parent_id` values to harvest private conversations.
The attack does not require any special privileges beyond a standard user account, and the attacker can remain undetected as the requests appear legitimate.
Protection:
The only complete mitigation is to upgrade to Open WebUI version 0.10.0 or later, where the channel‑context binding is enforced. For organisations unable to upgrade immediately, the following temporary measures can reduce risk:
– Input validation: Implement a reverse proxy or Web Application Firewall (WAF) rule that inspects requests containing `parent_id` and blocks those where the channel ID does not match the expected pattern.
– Monitoring: Enable detailed logging for all thread‑related endpoints and set up alerts for repeated `parent_id` access attempts across different channels.
– Access control review: Audit all channel‑based endpoints to ensure similar binding checks are in place.
– Least privilege: Restrict user permissions to the minimum necessary, and consider disabling private channel creation until the patch is applied.
Impact:
Successful exploitation allows an authenticated attacker to read message threads from private channels and direct messages they are not authorised to access. This can lead to the disclosure of confidential business discussions, sensitive user communications, proprietary information, and personally identifiable data shared within restricted channels. The vulnerability breaks the fundamental security boundary of channel isolation, eroding user trust and potentially exposing organisations to regulatory and compliance violations. While the CVSS score is LOW (3.1) due to the high attack complexity and limited confidentiality impact, the real‑world risk can be significant in environments where private channels contain highly sensitive information.
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Sources:
Reported By: nvd.nist.gov
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