CVE-2026-28788 Open WebUI's process_files_batch() endpoint missing ownership check, allows unauthorized file overwrite
Authenticated users can overwrite shared knowledge base files due to missing ownership checks, allowing control over LLM responses for other users.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-28788?
CVE-2026-28788 is a high-severity missing authorization vulnerability in Openwebui Open Webui, published on 26 Mar 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Official description
Open WebUI is a self-hosted artificial intelligence platform designed to operate entirely offline. Prior to version 0.8.6, any authenticated user can overwrite any file's content by ID through the `POST /api/v1/retrieval/process/files/batch` endpoint. The endpoint performs no ownership check, so a regular user with read access to a shared knowledge base can obtain file UUIDs via `GET /api/v1/knowledge/{id}/files` and then overwrite those files, escalating from read to write. The overwritten content is served to the LLM via RAG, meaning the attacker controls what the model tells other users. Version 0.8.6 patches the issue.
Weakness: CWE-639
Which versions are affected by CVE-2026-28788?
3 open source packages ship an affected version, including open-webui. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
open-webui PyPI | All versions | 0.8.6 |
open-webui PyPI | All versions | 0.8.6 |
open-webui PyPI | All versions | 0.8.6 |
Products include Openwebui Open Webui.
How do I fix CVE-2026-28788?
Upgrade open-webui to 0.8.6 or later.
Upgrade, and check permissions on every request on the server, not only in the interface. More about Missing authorization.
Is CVE-2026-28788 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-28788 exists.
Other vulnerabilities in Openwebui Open Webui
- CVE-2026-44551 Open WebUI: LDAP Empty Password Authentication Bypass
- CVE-2026-56400 open-webui - Remote Code Execution via CORS Misconfiguration and Session Validation
- CVE-2024-8017 Cross-site Scripting (XSS) in open-webui/open-webui
- CVE-2026-45672 Open WebUI: Jupyter code execution works despite `ENABLE_CODE_EXECUTION=false` — feature gate bypassed
- CVE-2026-87995 Open WebUI: Same-origin XSS to account takeover via terminal port-preview iframe hardcoding allow-same-origin
Sources
Also known as GHSA-jjp7-g2jw-wh3j, PYSEC-2026-2742.