GHSA-gfm2-xm6c-37qc CVE-2026-45349 PYSEC-2026-2726
Open WebUI has Broken Access Control for Completions API
- Severity
- 7.1 / 10
- High · CVSS 3.1
- Exploit chance (EPSS)
- 0.23%
- Chance of exploitation in the next 30 days. Higher than 14.08% of scored vulnerabilities.
- Known exploited
- No
- Not in CISA's catalog
- Weakness
- CWE-639 Authorization Bypass Through User-Controlled Key
- Fix
0.9.0- Upgrade open-webui to this version or later
Description
Summary
Any user X can continue the conversation of any other user Y, as long as the Chat ID of Y is known. User X does not even need to be an admin to do so.
Details
A user just needs to use the API endpoint: /api/chat/completions with their own API key (generated in OWUI) and the Chat ID of another user. OWUI does not check to match the Chat ID with the user that created that Chat ID. Note that both users will need access to the same model. This is especially relevant if there is a shared pipeline model between users.
PoC
- Using OWUI v0.6.18
- Sign in with any user
X - Generate an API Key for user
Xusing the settings - Create another user
Y, and have a conversation in OWUI. Copy the Chat ID from the URL. - User
Xcan now use the API/api/chat/completionsand the Chat ID from step 4 to continue the conversation of userY
Impact
Large impact to any user in OWUI. People can read your conversations, and access private information if they know your Chat ID (which is in the URL of the chat).
Resolution
Fixed in commit cf4218e68, first released in v0.9.0 (Apr 2026). The chat_completion handler at backend/open_webui/main.py:1868 now explicitly verifies chat ownership via Chats.is_chat_owner(chat_id, user.id) for any request that targets an existing chat, and raises 404 for non-owners (admin bypass preserved per the documented threat model). New chats (no chat_id supplied, or freshly inserted via the is_new_chat branch) are unaffected. Users on >= 0.9.0 are not affected.
Affected versions
PyPI
| Package | Vulnerable | Fixed in |
|---|---|---|
| open-webui | < 0.9.0 |
0.9.0 |
How to fix
Move to the fixed version or later with your package manager, update the lockfile, and run your tests. If the package only arrives through another dependency, upgrade that dependency first. If none of its releases pulls a fixed version yet, force the version with your package manager's override.
open-webui PyPI → 0.9.0
- pip
pip install --upgrade "open-webui>=0.9.0"- poetry
poetry add "open-webui>=0.9.0"- uv
uv add "open-webui>=0.9.0"
Severity breakdown
CVSS 3.1 7.1
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:L/A:N
- Attack vector
- Network
- Attack complexity
- Low
- Privileges required
- Low
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- High
- Integrity
- Low
- Availability
- None
Weakness
CWE-639: Authorization Bypass Through User-Controlled Key
The system's authorization functionality does not prevent one user from gaining access to another user's data or record by modifying the key value identifying the data.
How to prevent it
- Architecture and Design: For each and every data access, ensure that the user has sufficient privilege to access the record that is being requested.
- Architecture and Design, Implementation: Make sure that the key that is used in the lookup of a specific user's record is not controllable externally by the user or that any tampering can be detected.
- Architecture and Design: Use encryption in order to make it more difficult to guess other legitimate values of the key or associate a digital signature with the key so that the server can verify that there has been no tampering.
References
Advisories
Packages
Other links
Timeline
- Published
- Last updated by the source
- Latest EPSS score
Related advisories
| Advisory | Severity | Why it's related |
|---|---|---|
| GHSA-wvm9-9g5j-623f Open WebUI: Users denied by the OAuth role policy can still sign in via token exchange | Medium | Also affects open-webui |
| GHSA-4qg5-cxx4-g927 Open WebUI: Users denied by the OAuth domain allowlist or role policy can still sign in via token exchange | Medium | Also affects open-webui |
| GHSA-jqhh-cjmq-vmv6 Open WebUI: Any authenticated user can hang the server via a cyclic chat message history | Medium | Also affects open-webui |
| GHSA-5x7x-4c3c-qf5w Open WebUI: Server-side fetches reach blocked and internal hosts via unvalidated HTTP redirect targets | Medium | Also affects open-webui |
| GHSA-3cgp-3cqx-j8w2 Open WebUI: Any authenticated user can hang the server via message deletion in a cyclic chat tree | Medium | Also affects open-webui |
| GHSA-34r3-9m95-vq73 Open WebUI: Any authenticated user can reach the Azure platform channel via server-side web fetch | High | Also affects open-webui |
| GHSA-2724-6cpj-gf3v Open WebUI: Non-admin users can delete admin-owned external knowledge connections via knowledge base deletion | High | Also affects open-webui |
| GHSA-3pf7-q2g3-wj28 Open WebUI: Any authenticated user can inject chats into another user's folder via chat completions | Medium | Also affects open-webui |
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